Fix md5 issue in recent Gnulib merge

Fix md5 issue in recent Gnulib merge

When configured --with-native-compilation, Emacs needs md5_stream.
Problem reported by Andy Moreton (Bug#50985#23).
* admin/merge-gnulib (GNULIB_MODULES): Add crypto/md5,
needed for --with-native-compilation.
(AVOIDED_MODULES): Avoid crypto/af_alg, since Emacs doesn’t
need to bother with kernel-supported cryptography algorithms.
* lib/gnulib.mk.in, m4/gnulib-comp.m4:
Regenerate by running admin/merge-gnulib.
* lib/md5-stream.c: New file, copied from Gnulib.