* agent/pksign.c (do_encode_eddsa): First argument is NBITs,
so that it can support Ed448, as well as Ed25519.
(agent_pksign_do): Follow the change.
* agent/sexp-secret.c (fixup_when_ecc_private_key): No fix-up needed
for Ed448, it's only for classic curves.
* common/openpgp-oid.c (oidtable): Add Ed448.
* common/sexputil.c (get_pk_algo_from_key): Ed448 is only for EdDSA.
* g10/export.c (match_curve_skey_pk): Ed448 is for EdDSA.
* g10/keygen.c (gen_ecc): Support Ed448 with the name of "ed448".
(ask_algo, parse_key_parameter_part): Handle "ed448".
* g10/pkglue.c (pk_verify): Support Ed448.
(pk_check_secret_key): Support Ed448.
* g10/sign.c (hash_for): Defaults to SHA512 for Ed448.
(make_keysig_packet): Likewise.