GitLab

This incorporates:
2016-11-27 md4,md5,sha*: tune for recent glibc _STRING_INLINE_unaligned
2016-11-21 snippet/c++defs: Simplify _GL_CXXALIAS_* macros.
* build-aux/snippet/c++defs.h:
* lib/md5.c, lib/sha1.c, lib/sha256.c, lib/sha512.c:
Copy from gnulib.