gpg: Change format for the key size in --list-key and --edit-key.

* g10/gpg.c (oLegacyListMode, opts, main): Add --legacy-list-mode.
* g10/options.h (struct opt): Add field legacy_list_mode.
* g10/keydb.h (PUBKEY_STRING_SIZE): New.
* g10/keyid.c (pubkey_string): New.
* g10/import.c (import_one, import_secret_one): Use pubkey_string.
* g10/keylist.c (print_seckey_info): Ditto.
(print_pubkey_info, print_card_key_info): Ditto.
(list_keyblock_print): Ditto.
* g10/mainproc.c (list_node): Ditto.
* g10/pkclist.c (do_edit_ownertrust, build_pk_list): Ditto.
* g10/keyedit.c (show_key_with_all_names): Ditto.  Also change the
format.
(show_basic_key_info): Ditto.
* common/openpgp-oid.c (openpgp_curve_to_oid): Also allow "ed25519".
(openpgp_oid_to_curve): Downcase "ed25519"
--

For ECC it seems to be better to show the name of the curve and not
just the size of the prime field.  The curve name does not anymore fit
into the "<size><letter>" descriptor (e.g. "2048R") and a fixed length
format does not work either.  Thus the new format uses

   "rsa2048"    - RSA with 2048 bit
   "elg1024"    - Elgamal with 1024 bit
   "ed25519"    - ECC using the curve Ed25519.
   "E_1.2.3.4"  - ECC using the unsupported curve with OID "1.2.3.4".

unless --legacy-list-mode is given.  In does not anymore line up
nicely in columns thus I expect further changes to this new format.

Signed-off-by: Werner Koch <wk@gnupg.org>

g10/options.h

@@ -177,6 +177,7 @@ struct
   int no_literal;
   ulong set_filesize;
   int fast_list_mode;
+  int legacy_list_mode;
   int ignore_time_conflict;
   int ignore_valid_from;
   int ignore_crc_error;