crypto: Update crypto.h for libgcrypt KDF functions

crypto: Update crypto.h for libgcrypt KDF functions

This commit introduces the necessary changes to crypto.h in preparation
for implementing Argon2 support via the generic KDF functions, _gcry_kdf_*():
  - add new GPG error types required by kdf.c,
  - declare _gcry_digest_spec_blake2b_512 to enable BLAKE2b-512 digest calculations,
  - define the gcrypt KDF algorithm IDs for Argon2,
  - add the prototypes of _gcry_kdf_*() functions.

Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Vladimir Serbinenko <phcoder@gmail.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>