Drop MINGW_FE, which I can't find any trace of, and instead detect and
use MinGW compilers.
This requires adding AC_CANONICAL_TARGET, to set $target_cpu.
This is now required as cygwin_build is defined in terms of
target_builddir.
(Note that in other subdirectories, the autoconf variable
target_builddir is AC_SUBST-ed as a side-effect of using a macro from
winsup/acinclude.m4, which is perhaps less than ideal)
Bump GPLv2+ to GPLv3+ for some files, clarify BSD 2-clause.
Everything else stays under GPLv3+.
New Linking Exception exempts resulting executables from LGPLv3 section 4.
Add CONTRIBUTORS file to keep track of licensing.
Remove 'Copyright Red Hat Inc' comments.
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
