FIXES in 2.4.2-BETA-3

Revised the LINUX support to conform to LINUX 1.2.8 with gcc 2.6.3
from the slakware distribution.

Fixed some minor source code cast that the SunPro C compiler was 
complaining about. Files affected (all in the src directory) are:
ftpcmd.y, realpath.c, private.c, logwtmp.c, ftpd.c extensions.c

Created the NOTES file and revised the README and INSTALL documents.
