Import crypto/md5 module from gnulib.

Import crypto/md5 module from gnulib.

* Makefile.in (MAKEFILE_MODULES): Add crypto/md5.
* admin/notes/copyright: Remove src/md5.c and src/md5.h as
special cases.
* src/Makefile.in (base_obj): Remove md5.o, since this file
is in lib now.
* src/deps.mk (md5.o): Remove.
* aclocal.m4, configure, lib/Makefile.in, lib/gnulib.mk, m4/gl-comp.m4:
Regenerate.
* lib/md5.c: Regenerate.  This renames the file from src/md5.c,
and adds some porting improvements from gnulib.
* lib/md5.h: Regenerate, likwise; rename from src/md5.h.
* m4/md5.m4: New file, from gnulib.

2011-02-18  Paul Eggert  <eggert@cs.ucla.edu>