* cipher/cipher-gcm.c (do_ghash_buf): Proper handling for the case
where 'unused' gets filled to full blocksize.
(gcm_crypt_inner): New.
(_gcry_cipher_gcm_encrypt, _gcry_cipher_gcm_decrypt): Use
'gcm_crypt_inner'.
* cipher/cipher-internal.h (cipher_bulk_ops_t): Add 'gcm_crypt'.