md: Optimize gcry_md_hash_buffers for SHA-256 and SHA-512.
* cipher/sha256.c (_gcry_sha256_hash_buffer): New. (_gcry_sha256_hash_buffers): New. * cipher/sha512.c (_gcry_sha512_hash_buffer): New. (_gcry_sha512_hash_buffers): New. * cipher/md.c (_gcry_md_hash_buffer): Optimize for SHA246 and SHA512. (_gcry_md_hash_buffers): Ditto.
- Signed-off-by: Werner Koch <wk@gnupg.org>