Sync from coreutils.

Sync from coreutils.
* md5.c: Fix commentary typos.
(OP): Fix spacing.
(alignof, UNALIGNED_P): No need for a GCC-specific version.
* md5.h (__attribute__): Remove; unused.
* sha1.c: Fix commentary to match md5 better.
* sha1.h (struct sha1_ctx): Use a word buffer, not a byte buffer,
so that we don't need to worry about alignment.  All uses changed.
This merges the 2005-10-28 md5 change into sha1.