Let gf2x use --libdir and make SAGE_FAT_BINARY work.
Replace symlink in a more portable way.
Make generic build of gf2x smarter.
More fixes for gf2x generic build.
Support SSE2 on x86_64 for gf2x.
Simplify generic build of gf2x.
Properly autoreconfed patches.
Document new gf2x patch.
Prevent autotools to regenerate files.
Simplify gf2x patches
Make the SSE2 stuff work if the compiler does not support SSE2.
Improve sse2/pclmul detection and enabling
Merge remote-tracking branch 'trac/develop' into ticket/15316
Update git branch for gf2x SSE2 and Cygwin fixes.
Trac #15316: Make gf2x respect SAGE_FAT_BINARY and use --libdir

When SAGE_FAT_BINARY is set we should pick a generic value for hwdir.
We should also use --libdir so that gf2x works ok on OpenSuse and
similar systems.

'''Upstream''': [https://gforge.inria.fr/tracker/index.php?func=detail&a
id=16566&group_id=1874&atid=6979]

URL: http://trac.sagemath.org/15316
Reported by: jpflori
Ticket author(s): Jean-Pierre Flori, Erik Massop
Reviewer(s): Jeroen Demeyer, Jean-Pierre Flori
Updated Sage version to 6.4.1