2.10.0 (stable):

* Build: Fix silent builds.
  (Kjell Ahlstedt) Bug #768797

2.9.3 (unstable):

* signal:
  Deprecate slots().
  Please tell us if you really need this.
  (Murray Cumming)
  Deprecate emit_reverse().
  Please tell us if you really need this.
  (Murray Cumming)
* Benchmark: Update it and use boost::timer, and actually build it,
  but not built by default.
  (Murray Cumming)

Build:
* Fix the build on MSVC++ 2013 and 2015.
  (Chun-wei Fan) Bug #767777


2.9.2 (unstable):

* Minor documentation improvements.
  (Murray Cumming)
* Some more minor uses of C++11 syntax.
  (Murray Cumming)


2.9.1 (unstable):

* slot: Allow sigc::slot<R(Args...)> syntax, like std::function,
  deprecating the sigc::slot<R, Args...> syntax.
  (Murray Cumming, Kjell Ahlstedt) Bug #763393
* signal: Allow sigc::signal<R(Args...)> syntax, like std::function,
  deprecating the sigc::signal<R, Args...> syntax.
  (Murray Cumming, Kjell Ahlstedt) Bug #763393


2.8.0 (stable):

* Documentation: Mention use with CMake.

2.7.2 (unstable):

* Deprecate sigc::ref() and sigc::reference_wrapper(),
  adding support instead for std::ref(), std::cref(),
  and std::reference_wrapper().
  (Murray Cumming)
* mem_fun(): Deprecate mem_fun(pointer, func).
  Leaving just mem_fun(reference, func).
  Please let us know if you disagree strongly with this.
  (Murray Cumming) Bug #763215
* Make all operator bool() explicit. (A C++11 feature.)
  (Murray Cumming)
* Build: Remove some now-unnecessary configure checks.
  But please let us know if this causes problems for you.
  (Murray Cumming) Bug #762065 (Kjell Ahlstedt)
* Build: Update MSVC project.
  (Chun-wei Fan)
* Documentation: Improve the documentation of mem_fun(), making it clear that
  mem_fun() does not return a slot.
  (Kjell Ahlstedt)

2.7.1 (unstable):

* signal: Add a moving connect() method, taking an rvalue reference
  to a slot.
  (Kjell Ahlstedt) Bug #756484
* can_deduce_result_type_with_decltype: Rename the check() methods to
  checksize(). check() is a preprocessor macro in Mac OS X.
  (Kjell Ahlstedt) Bug #759315 (David Otto)
* Temporarily undefine the nil macro, if it's defined.
  nil is a preprocessor macro in Objective-C++ and Mac OS X.
  (Kjell Ahlstedt) Bug #695235
* Correct the mem_functor<> declarations.
  Murray Cumming

2.6.2 (stable):

* slot: Handle auto-disconnection when a slot contains a slot
  (Kjell Ahlstedt) Bug #755003 (Ryan Beasley)
* slot and signal: Correct move constructors and move assignments.
  (Kjell Ahlstedt) Bug #756484.
* trackable, slot_base, signal_base, connection: Add some noexcept specs
  (Kjell Ahlstedt) Bug #756484.
* trackable, slot, signal: Remove noexcept from move operations.
  (Kjell Ahlstedt) Bug #756484.
* slot and signal: Add missing move constructors and move assignments
  (Kjell Ahlstedt) Bug #756484.
* signal_impl: =delete copy and move operations.
  (Murray Cumming, Kjell Ahlstedt) Bug #756484
* typed_slot_rep: =delete unimplemented copy and move operations.
  (Murray Cumming, Kjell Ahlstedt) Bug #756484
* slot_rep: =delete copy and move operations.
 (Murray Cumming, Kjell Ahlstedt) Bug #756484


2.6.1 (stable):

* Add back deprecated adaptors/lambda API to avoid an unintented ABI break.
  (Kjell Ahlstedt) Bug #755550 (Michael Biebl)
* sigc::trackable: Move operations: Don't move the callback list
  (Kjell Ahlstedt) Bug #755393 (Tom Schoonjans)


2.6.0 (stable):

* C++11: deduce_result_type: Simplify with C++11 variadic template.
  (Murray Cumming, Marcin Kolny) Bug #753612
* Fix the build with MSVC.
  (Chun-wei Fan) Bug #754082
* Update the website.
  (Kjell Ahlstedt)


2.5.4 (unstable):

* slot_base::operator=(const &): Copy the blocked too,
  so the destionation is blocked if the source is blocked,
  regardless of whether the destionation was previously
  blocked, because this seems to be what we should expect.
  (Murray Cumming)
* C++11: slot_base, slot*, signal_base, signal*, trackable:
  Add move operations.
  (Murray Cumming)
* Update MSVC Projects, requiring at least MSVC++ .Net 2013
  for C++11 support.
  (Chun-wei Fan)


2.5.3 (unstable):

* Use C++11 "using" aliases to simplify code that uses type traits.
  (Murray Cumming) Bug #753580


2.5.2 (unstable):

* Remove useless headers:
    sigc++/class_slot.h
    sigc++/hide.h
    sigc++/method_slot.h
    sigc++/object.h
    sigc++/object_slot.h
    sigc++/retype.h
  Some of these still have equivalents in sigc++/adaptors/
  (Kjell Ahlstedt, Murray Cumming) Bug #752560
* C++11: Replace deprecated std::auto_ptr by std::unique_ptr.
  (Kjell Ahlstedt)
* C++11: Use std::is_base_of<> instead of our sigc::is_base_and_derived<>,
  removing sigc::is_base_and_derived<>.
  (Kjell Ahlstedt, Murray Cumming) Bug #752560
* C++11: Use of range-based for loops.
  (Murray Cumming)
* C++11: Use of the auto keyword.
  (Murray Cumming)
* C++11: Use of nullptr instead of 0.
  (Murray Cumming)
* sigc++/slot.h: Use a regular .h file instead of generating it
  from an .m4 file. Bug #752560
  (Kjell Ahlstedt)
* Visual Studio Builds: Move 2010 Projects to 2012 to support C++11.
  (Chun-wei Fan)
* Use -Wformat-security and -Wshadow with --enable-warnings=fatal.
  (Murray Cumming)


2.5.1 (unstable):

* Use (and require) C++11
  (Kjell Ahlstedt) 
* Using C++11 lambda functions to create sigc::slots:
  Avoid the need for SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE.
  (Kjell Ahlstedt)
* Remove the already-deprecated sigc::lambda (and sigc::group) API.
  This is an API change but should not be an ABI change, so it should
  only affect you when rebuilding applications, if you use this API.
  (Murray Cumming, Kjell Ahlstedt)


2.4.1 (stable):

* A slot's functor is destroyed when an empty slot is assigned to the slot.
  (Kjell Ahlstedt) Bug #738602 (James Lin)
* test_disconnect_during_emit tests that the slot is really disconnected
  during signal emission.
  (Kjell Ahlstedt)

2.4.0 (stable):

Note: API/ABI is the same as in release 2.3.2. Compared to stable
releases 2.2.x, the API has been broken regarding visit_each() functions.
See the NEWS entry for libsigc++ 2.3.2.

* Fix the test_lambda test case for MS Visual C++ 2013 and other
  C++11-compliant compilers.
  (Kjell Ahlstedt) Bug #734368 (Ryan Beasley)
* Add a missing #include in limit_reference.h.
  (Kjell Ahlstedt)
* Documentation:
  - Use doxygen-extra.css from the mm-common package.
    Requires mm-common 0.9.7 when configured to use maintainer-mode.
    (Kjell Ahlstedt)

2.3.2 (unstable):

Note: The implementation of bug #724496 breaks API for some users,
but it does not break ABI.
Only users who have added their own visit_each() overloads are affected by
the API break. Their programs will still compile, but there will be run-time
errors, if they rely on auto-disconnection of slots.
Updated instructions for users who implement their own adaptors are found
in the description of sigc::adapts<>. 

* Replace visit_each() overloads by struct visitor<>.
  Add the test_visit_each test case.
  (Ryan Beasley, Kjell Ahlstedt) Bug #724496
* signal_impl::notify(): Don't delete signal_impl during erase().
  (Kjell Ahlstedt) Bug #564005 (Alexander Shaduri)
* Fix 'make check' with clang++ 3.4 and --enable-warnings=fatal
  (Kjell Ahlstedt) Bug #724496 (Ryan Beasley)
* Fix test_cpp11_lambda for gcc 4.8
  (Kjell Ahlstedt)
* Speed up disconnection of slots.
  (Kjell Ahlstedt) Bug #167714 (Neal E. Coombes)
* Auto-generate the ChangeLog from the git log for 'make dist'.
  (José Alburquerque)
* Don't use __file__ in the FIREWALL m4 macro.
  (Kjell Ahlstedt) Bug #699168 (John Ralls)
* Add the track_obj() adaptor and test_track_obj test case.
  Deprecate libsigc++ lambdas, sigc::group() and sigc::var().
  Use C++11 lambda expressions instead.
  (Kjell Ahlstedt) Bug #672555
* Documentation:
  - Emphasize that signals are reference counted.
    (Kjell Ahlstedt) Bug #611941 (Jonathon Jongsma)
  - Mention std::function<> and std::bind() where appropriate.
    (Kjell Ahlstedt, Chris Vine)
  - Use DOXYGEN_SHOULD_SKIP_THIS consistently to exclude internal
    functions from the reference documentation.
    (Kjell Ahlstedt)
* Windows:
  - Enable C++11 lambda expressions with MS Visual Studio 2012 and later
    (Ryan Beasley) Bug #733752
  - Update MSVC_Net2010
    (Kjell Ahlstedt) Bug #724496 (Ryan Beasley)

2.3.1 (unstable):

* signal_base: Add blocked(), block(), unblock().
  (Kjell Ahlstedt) Bug #153780

2.2.11 (stable):

* Fix comma operator in libsigc++ lambda expressions.
  Andris Pavenis) Bug #342911
* Added SIGC_FUNCTORS_DEDUCE_RESULT_TYPE_WITH_DECLTYPE.
  This allows most uses of libsigc++'s lambda expressions to be 
  replaced by standard C++11 lambda expressions.
  (Kjell Ahlstedt) Bug #672555.
  Thanks to Chow Loong Jin, who posted similar code on libsigc-list.
* Use std::size_t and std::ptrdiff_t instead
  (Kjell Ahlstedt)
* Fix 'make check' with gcc 4.7.
  (Kjell Ahlstedt)
* Enable test_lambda in 'make check'.
  (Kjell Ahlstedt) Bug #669128.


2.2.10:

* slot_rep: Avoid access to deleted object in notify(),
	and test case.
	(Kjell Ahlstedt ) Bug #564005 (Alexander Shaduri)
* Mention visit_each() in the documentation of sigc::adapts.
  (Thomas Rydzynski)
	
2.2.9:

* trackable: Avoid calling the same callback function twice, fixing some
	memory corruption.
	(Kjell Ahlstedt) Bug #589202
* Minor documentation corrections.
  (David King)
* Fix the build with GCC 4.6
	(Kalev Lember)
* Windows build fixes for MSVC++ .Net 2005 and 2010
  (Armin Burgmeier)

2.2.8:

Nothing interesting. Just a small change for library.gnome.org.

2.2.7:

* Documentation:
  - Added main page text with doxygen.
  (David King, Murray Cumming)
  - Fix the functors Doxygen group.
  (David King)
  - Tutorial: Removed outdated marshallers section that had no working example.
  (Murray Cumming) Bug #417924 (Michael Ekstrand)

2.2.6:

* Slight documentation changes.
  (Murray Cumming) Bug #614741 (Armin Burgmeier)

2.2.5:

* Accumulators: Allow return types that are different to the signal's.
  (Krzysztof Kosiński)
* Documentation:
  - Disable collaboration graphs in documentation
  - Use non-blurry font for graph labels.
  (Daniel Elstner)
  - sigc::hide() correction: It always only hides one signal argument.
  (Michael Hasselmann)
* Fix the MSVC++ build.
  (Armin Burgmeier)

2.2.4.2 (stable):

* Namespace sigc is now documented, in order to make large chunks of the
  reference reappear.  (Daniel Elstner)
* The shipped reference documentation has been regenerated using Doxygen
  1.6.1, so that the document type is now XHTML 1.0.  (Daniel Elstner)
* The shipped Devhelp file has been generated with a newer version of the
  XSLT script in mm-common, so that documentation groups no longer appear
  as namespace prefixes in the keyword list.  (Daniel Elstner)

2.2.4.1 (stable):

* Reenable the per-class hierarchy graphs in the reference documentation.
  (Daniel Elstner)
* Drop the custom HTML header and footer, and use the shared doxygen.css
  file from mm-common. (Daniel Elstner)

2.2.4 (stable):

* New build system based on mm-common. The mm-common module is now
  required for building from the git repository, but not for builds
  of release archives. (Daniel Elstner)
* The public reference documentation is now hosted on library.gnome.org.
  (Frédéric Péters, Daniel Elstner)

2.2.3 (stable):

* Windows:
  - Added project files (and property sheets) for
  MSVC++ 2005 and 2008.
  (Armin Burgmeier)
  - Removed unnecessary dependency on afxrefs.h, so it builds
  with MSVC++ Express editions.
  (Cedric Gustin)

2.2.2 (stable):

* Added an include of functors/slot.h that was mistakenly removed
  during the 2.1 series.
  (Deng Xiyue) Bug #521418.

2.2.1 (stable):

* Really fix the build with Sun CC.
  (Elaine Xiong. Bug #302098)

2.2.0 (stable):

* Build fixes when using gcc 4.3 pre-releases.
  (Ryan Hill, Vladimir Marek)

2.1.1 (unstable):

WARNING: This is an unstable release and should not yet be
packaged by distributions unless libsigc++ 2.0.x does not
build for some reason (Please report such bugs).

* Removed the SigC:: namespace and other compatibility API,
  to fix the build with some versions of some compilers,
  such as the SUN Forte C++ CC compiler.
  See bug #302098, for instance
  (Murray Cumming)
* sigc::signal<>:
  - Added Added typedefs for
  value_type, reference, and pointer, so that these
  iterators are more like standard C++ iterators, so they can
  be used with standard C++ algorithms.
  (Michael Elkstrand) (Bug #417926).
  - Added emit_reverse().
  (John Profic)

2.0.17:

* slot::disconnect(): Make this work.
  sigc::connection::disconnect() already worked.
  (James Lin, Murray Cumming)
* visit_each compilation problem fixed.
  (Philipp Berndt)

2.0.16:

* Fixed build for SUN Forte C++ 5.5
* Fixed build for MSVC++ 7.1
* Fixed crash when using --no-inline with g++.

2.0.15:

* g++ 3.2 (and Mac OS X g++ 3.3) build fix.
  (Paul Pogonyshev)
* Compose: Fix slot lifetime regression introduced in
  2.0.9. (Philip Langdale)
* tests: Small ISO C++ correctness fix (Marek Rouchal)
* Don't specify unused function parameter names.
  (Andris Pavenis)

2.0.14:

* SUN Forte 5.7 build fix for ambiguity when using
  inner template class. However, you still need the
  patch in bug #302098 to finish the build.

2.0.13:

* signal_emit::emit(): Ensure the correct order of
  destruction of the member variables, to avoid a leak.
  (Andreas Ames, bug #306249)
* Allow recursive signal emission again.
  (Neal E. Coombes, bug #303896)
* SUN Forte CC 5.5 build fixes:
  - test_compatibility minor fix.
  - visit_each() template specializations:
  Mention the bool I_derives_trackable template type,
  (Friedemann Kleint, bug #305647)
 - Check for the non-standard SUN reverse_iterator,
  and use alternative code if necessary.
  (Murray Cumming)

2.0.12:

* Fixes crashes when using virtual inheritance, particularly
  with bound by-reference parameters, caused by casting
  from derived to base when the derived destructor has run.
  (Régis Duchesne)
  This might affect non-g++ compilers, so do tell us about
  any problems.

2.0.11:

* Build fixes for SUN Forte, Tru64
  (Murray Cumming), and MSVC++ (Cedric Gustin).

2.0.10:

* tests: Include <new> to avoid unresolved symbols on Tru64.
  (Tim Mooney)
* When signal handlers are connected made during an emit
  of the same signal, prevent them from being called in the
  same emit, to prevent infinite loops.
  (Neal E. Coombes)
* Performance improvement in a corner case.
  (Neal E. Coombes).

2.0.9:

* sigc::bind() now works with the AIX and Tru64 compilers.
  See the comments in sigc++/visit_each.h: visit_each_type()
  if you have compilation problems.
  (Murray Cumming)
* sigc::var() is now documented. (Roger Ferrer Ibáñez)

2.0.8:

* Maybe avoid (incorrect) warning with g++ 3.3.5.
  (Murray Cumming)
* Fix namespace ambiguity when using multiple
  major versions of libsigc++. (Liza Klerck)

2.0.7:

* Now builds with the following compilers, in addition to
the existing GNU g++, SUN Forte CC 5.5, MSVC++ .Net 2003,
and Intel compilers:
- IBM AIX xlC v7
- Tru64 C++ V6.5-042
- IRIX MIPSpro 7.4.2m
  (Older versions of all these compilers might also work.)
  (Murray Cumming, www.thewrittenword.com)
* MSVC++ .Net 2003 build improvements.
  (Cedric Gustin, Timothy M. Shead)
* Replace C-style casts with reinterpret_cast<> and
  static_cast<>. (e97_far at e.kth.se).
* Documentation: Added manual, based on the manual in
  libsigc++ 1.2, but updated for the new API.
  (Murray Cumming)


2.0.6:

* Fixed a memory leak in sigc::slot.
* Fixed compilation for gcc-3.4.
* Fixed compilation for Intel C++ compiler (upgraded libtool).
* Fixed project files for MSVC .Net (Timothy M. Shead).
* Fixed segfaults when compiled with MSVC .Net 2003 (moved
  all calls to new and delete into non-inline library code).
* In the compatibility module use correct bound_mem_functor
  variants for const (volatile) methods when creating a slot.
* Minor documentation fix.
* Resolved bugs: #152327 #148744 #152323 #151404 #153143

2.0.5:

* Distribute pregenerated configuration header for MSVC .Net.

2.0.4:

* Fixed warnings and compiler errors in the test cases.
* Added a new test case (Murray Cumming).
* Fixed 'hello_world' example.
* Don't test optional features that fail with the Sun FORTE.
* Fixes for the Sun FORTE to compile out-of-the-box
  (Damien Carbery, Murray Cumming, Martin Schulze).
* Fixes for MSVC to build a DLL out-of-the-box (James Lin).
* Improved compiler specific configuration during 'configure'.
* Added rmp description file libsigc++-2.0.spec (Eric Bourque).
* Minor documentation improvements (Murray Cumming).
* Resolved bugs: #147311 #147313 #147391 #144846 #145541

2.0.3:

* Fix segfault on emission of unconnected signal.
* Test emission of unconnected signals in the test case.
* Suppress compiler warning at dynamic_cast<>-test for good.
  (Help from Christof Petig and Timothy M. Shead.)

2.0.2:

* Suppress compiler warning in compatibility module at
  dynamic_cast<>-test (fix suggested by Timothy M. Shead).
* If a custom accumulator is specified invoke it on signal
  emission even if the signal's slot list is empty. (This used
  to be the case in libsigc++-1.2 as pointed out by Timothy.)

2.0.1:

* Fixed serious bug in reference counting in sigc::signal_base::impl().
* Fixed SigC::Object-derivation check in SigC::slot() compatibility module.
* Fixed compilation on Apple gcc 3.3 (assisted by Spundun Bhatt).
* Fixed configure check for gcc 3.4 (Murray Cumming).

2.0.0:

* Implemented sigc::connection::blocked() (Murray Cumming).
* Added the scripts directory to the make dist target (Murray Cumming).
* Added more documentation (Martin Schulze).

1.9.16:

* Fixed compiler warning in sigc::connection (Alexander Nedotsukov, Murray Cumming).
* Fixed examples and made them part of the regular build (Murray Cumming).
* Added header sigc++config.h for configure time checks (Murray Cumming).
* Added configure time checks to determine the correct syntax
  for explicit template method specializations (Murray Cumming).
* Removed code using partial specializations of overloaded template methods
  from test cases. SUN Forte doesn't support this feature (Martin Schulze).
* Fixed compilation for gcc 3.4 (Murray Cumming).

1.9.15:

API additions:
* Add numbered slot# templates.
* Allow for methods of the object's base types to be passed into sigc::mem_fun().

Other fixes and cleanups:
* Make is_base_and_derived template compatible with the SUN Forte.
* Non-template code moved from .m4 macro source to .h/.cc files (Murray Cumming).
* Implementation moved to .cc files (Murray Cumming).
* More fixes for the SUN Forte. Make some more ctors explicit.

1.9.14:

* Added sigc::slot_base::operator bool() (Murray Cumming).
* Build docs directory by default (Murray Cumming).
* Fixed minor doxygen issues (Murray Cumming).
* Fixed compiler warning in signal.h (Murray Cumming).

1.9.13:

* Fixed passing references through sigc::slot (Reported by Jeff Franks).
* Enabled binding of objects to method slots through sigc::bind().
* Reworked sigc::bind() API: Made the template argument for the
  parameter position zero-based and optional. Added overloads for
  binding of up to 7 arguments at a time when no position is specified.
* Reworked sigc::hide() API: Made the template argument for the
  parameter position zero-based and optional.
* Fixed compilation problems with MSVC .Net 2003 (Roel Vanhout).
* Distribute MSVC .Net 2003 project files in the tarballs.
* Improved and extended documentation.
* Minor cleanups.

1.9.12:

* Added adaptor retype(). With this final API addition all adaptors
  are in place that are available in libsigc++-1.2.
* Added negation lambda operator. Use STL names for lambda actions.
* Remove formerly disabled support for gcc extension typeof().
* Added project files for MS Visual Studio .Net 2003. (Roel Vanhout)
* Make libsigc++2 compile with .Net 2003. (Roel Vanhout, Martin Schulze)
* Build shared version of libsigc++2 by default. (Cedric Gustin)
* Add support for win32 platform. (Cedric Gustin)
* Install .m4 files. (requested by Ron Steinke)
* Cleaned up functors.
* Restructured and completed documentation of the core library parts.

1.9.11:

API Additions and important bug fixes:
* Compatibility module completed. libsigc++-1.2 filenames are preserved.
* Fixed critical bug in auto-disconnection: don't defer detaching
  of a slot from all referred trackables during signal emission.
* Reduced size of slots significantly.
* Fixed support for sigc::ref() in adaptors.
* Fixed sigc::visit_each(): only hit targets that are passed by
  reference; pass bound members in bound_member_functor by reference.
* Add lambda actions sigc::{reinterpret,static,dynamic}_cast_
  to support explicit parameter conversion.
* Add adaptors sigc::retype_return<>() and sigc::hide_return().

Minor fixes:
* Fixed return type deduction for bind<0>.
  libsigc++-1.9.11 should compile with gcc-3.3.
* Fixed copy constructor and operator=() of slot template.
* Fixed a compiler warning in signal_emit#<>::emit().
* Improved test case.

1.9.10:

* Fix compiler issues with gcc-3.3.2 (patch from Jeff Franks).
* Remove compiler check for the gcc extension typeof().
* Simplify bind_functor templates.
* Move definition of struct nil into functor_trait.h.

1.9.9:

* Add a constructor to sigc::connection that takes a slot_base&
  to support user defined slot lists like they are used in gtkmm.
* Fix compiler issues with gcc-3.3.2 (reported by Jeff Franks).

1.9.8:

* Add compatibility module that defines namespace SigC.
  namespace SigC should be API compatible to libsigc++-1.2.
  Currently only the core parts of the library are supported.
  Adaptors are still to follow.
* Fix connection::operator=(). Include connection.h in sigc++.h.
* Get rid of namespace functor.
* Rename dependency to destroy_notify_callback.
* Rename trackable::clear() to trackable::notify_callbacks().
* Move slot_base, signal_base, slot_iterator[_buf], slot_list
  out of namespace internal. They are public API.
* Add reference counter to signal_impl enabling signals
  to share the underlying information.
* Add convenience function signal#::make_slot().
* Get rid of one-letter-parameter-names.
* Get rid of "using namespace ..." in the test cases.
* Add lambda operators subscript ([]) and assign (=).
* Fix is_base_and_derived<> for const types.
* New and updated documentation.
* Add previous announces to file NEWS.

1.9.7:

* Added sigc++/sigc++.h. (Murray Cumming)
* Added member_method example. (Murray Cumming)
* Renamed closure to slot.
* Fixed issues with gcc-3.3. (Adreas Rottmann)
* Removed unnecessary void specializations.
* Made adaptors' operator()() (overload with no arguments) return a value.
* Made visit_each() support adaptors.
* Overhauled return type deduction to make it work without typeof().
* Added convinience macros SIGC_FUNCTORS_HAVE_RESULT_TYPE and
SIGC_FUNCTOR_TRAIT(T_functor, T_result) to make return type deduction system
support 3rd-party funtors.
* Changed syntax of group adaptor from "[functor] % grp([lambdas])" to "group
([functor], [lambdas])".
* Made many fixes to lambda functionality.
* Added var() and constant() lambda creators.
* Added many lambda operators.
* Added ref() which creates a reference wrapper to enable storage of
references in bind and group adaptors.
* Expanded test suite.
* Added documentation. (Corrections by Murray Cumming)

1.9.6:

* First public release of the unstable 2.0 generation.
  libsigc++ 2.0 uses modern C++ mechanisms to achieve a highly
  flexible, yet typesafe callback system. It supports all features of
  libsigc++ 1.2 and improves upon it by:
  - No need to specify the number of arguments in signal definitions.
  - Connection of any compatible (=implicitly convertable) functor
   to a signal.
  - Implicit type conversions of parameters during signal emission.
  - Lambda adaptor for complete restructuring of functor parameter
   lists in one line (subject to changes).
  - Signal has a fully featured stl style list interface.
  - A convinient accumulator API (replacing the old marshaller API).
  - Removal of unnecessary memory management functionality.
  - Lightweight class "trackable" for use as base class of your
   class hierarchy replaces class "Object".
