* common/util.h (openpgp_curve_to_oid): Add new argument to select OID
by OpenPGP version.
* common/openpgp-oid.c (openpgp_curve_to_oid): Implement returning
selected OID for Curve25519.
* common/openpgp-fpr.c (compute_openpgp_fpr_ecc): Follow the change,
selecting by the version.
* g10/export.c (match_curve_skey_pk): Likewise.
(transfer_format_to_openpgp): Likewise.
* g10/gpg.c (list_config): Likewise, print new OID.
* g10/keygen.c (ecckey_from_sexp): Likewise, selecting by the version.
* sm/encrypt.c (ecdh_encrypt): Likewise, don't care.
* sm/minip12.c (build_ecc_key_sequence): Likewise, new OID.
* scd/app-openpgp.c (ecdh_params, gen_challenge): Likewise, don't
care.
(ecc_read_pubkey, change_keyattr_from_string, ecc_writekey): Likewise,
old OID.