gpg: Add option --with-subkey-fingerprint.

* g10/gpg.c (oWithSubkeyFingerprint): New.
(opts): Add --with-subkey-fingerprint[s].
(main): Set that option.
* g10/options.h (struct opt): Add 'with_subkey_fingerprint'.
* g10/keylist.c (list_keyblock_print): Print subkey fingerprint.
(print_fingerprint): Tweak printing to use compact format if
desirable.

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

g10/keyid.c

@@ -384,6 +384,9 @@ keystrlen(void)
 
   switch(format)
     {
+    case KF_NONE:
+      return 0;
+
     case KF_SHORT:
       return 8;