* src/gcrypt.h.in (gcry_buffer_t): new.
(gcry_md_hash_buffers): New.
* src/visibility.c, src/visibility.h: Add wrapper for new function.
* src/libgcrypt.def, src/libgcrypt.vers: Export new function.
* cipher/md.c (gcry_md_hash_buffers): New.
* cipher/sha1.c (_gcry_sha1_hash_buffers): New.
* tests/basic.c (check_one_md_multi): New.
(check_digests): Run that test.
* tests/hmac.c (check_hmac_multi): New.
(main): Run that test.