o since the define 'VAX' was only used to tell that the byte order is
LITTLE_ENDIAN (it have nothing else to do with the VAX computer family)
it can safely replaced with '!WORDS_BIGENDIAN'.
o check if pointers are 64 bit
o replaced HAS_64BIT_POINTERS with 'SIZEOF_VOID_P == 8'
o autoconf v2.53 and later is now required to generate configure
(sorry, but it makes many tasks easier)
o improved tests for mmap, socklen_t and offt_64
o added tests for atexit, on_exit, (v)fork, set(p)grp, setpgid and flock
o added test for the keyword 'volatile'
o fixed errors in configure.in
o updated config.h.in and autoconfig_msvc.h (the latter may be incorrect)
o replaced VOLATILE by volatile
o removed SETPGRP and ATEXIT
o replaced NO_FLOCK by HAVE_FLOCK
o SIG_FPTR cleanup
o vfork cleanup
