architectures when using configure --with-archflags option, thus file config.h should not contain
architecture-dependent definitions.
The fix: 1) don't use autoconf's endianness determination procedure because it can't give a result
that fits both big and little endian architectures.
2) have config.h include a mac-specific file under Mac OS.
git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@8511 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
