agent: Replace es_mopen by es_fopenmem for ssh.

* agent/command-ssh.c (ssh_read_key_public_from_blob): Use
es_fopenmem.
(ssh_handler_request_identities): Ditto.
(ssh_request_process): Ditto.
--

es_fopenmem is easier to understand than the more general function
es_mopen.  Thus we better use the former for clarity.
Change some keyedit functions to allow printing to arbitrary streams.

* common/ttyio.c (tty_print_string): Add optional arg FP. Change all
callers.
(tty_print_utf8_string2): Ditto.
* g10/keyedit.c (show_prefs):  Ditto.
(show_key_with_all_names_colon): Ditto.
(show_names): Ditto.
* g10/keylist.c (print_revokers): Ditto.
(print_fingerprint): Ditto.
gpg: Add commands --quick-sign-key and --quick-lsign-key.

* g10/gpg.c (main): Add commands --quick-sign-key and
--quick-lsign-key.
* g10/keyedit.c (sign_uids): Add args FP and QUICK.
(keyedit_quick_sign): New.
(show_key_with_all_names): Add arg NOWARN.
agent: EdDSA support for SSH.

* agent/command-ssh.c (ssh_signature_encoder_eddsa): Signature is
two 32-byte opaque data which should not be interpreted as number.
g10: EdDSA support.

* g10/keyid.c (keygrip_from_pk): Compute keygrip of EdDSA key.
* g10/keygen.c (generate_subkeypair): Ed25519 is for EdDSA.
* common/openpgp-oid.c (oid_ed25519): Update.
agent: Support EdDSA.

* agent/pksign.c (agent_pksign_do): Handle EdDSA signature.