* cipher/ecc-eddsa.c (_gcry_ecc_eddsa_compute_h_d, _gcry_ecc_eddsa_sign)
(_gcry_ecc_eddsa_verify): Use same _gcry_md_hash_buffers_extract code
path for SHA512 and SHAKE256.
* cipher/md.c (_gcry_md_hash_buffers): Rename to ...
(_gcry_md_hash_buffers_extract): ... this; Add digestlen and handling
for XOF algorithms (SHAKE128, SHAKE256).
(_gcry_md_hash_buffers): New.
* src/gcrypt-int.h (_gcry_md_hash_buffers_extract): New.