g10: Use canonical name for curve.
* g10/import.c (transfer_secret_keys): Use canonical name. * common/openpgp-oid.c (openpgp_curve_to_oid): Return NULL on error. * g10/keyid.c (pubkey_string): Follow change of openpgp_curve_to_oid. * g10/keylist.c (list_keyblock_print, list_keyblock_colon): Ditto. * g10/parse-packet.c (parse_key): Ditto.