* g10/options.h (opt): Add show_only_session_key and turn
show_session_key into a bit flag.
* g10/gpg.c (oShowOnlySessionKey): New.
(opts): Add "show-only-session-key".
(main): Set flag.
* g10/mainproc.c (proc_encrypted): Handle the new option.
* g10/decrypt-data.c (decrypt_data): Ditto.  Add compliance error flag
to the DECRYPTION_INFO status line.