gpgsm: Add command option "offline".

* sm/server.c (option_handler): Add "offline".
(cmd_getinfo): Ditto.
* sm/certchain.c (is_cert_still_valid):
(do_validate_chain):
* sm/gpgsm.c (gpgsm_init_default_ctrl): Default "offline" to the value
of --disable-dirmngr.
* sm/call-dirmngr.c (start_dirmngr_ext): Better also check for
ctrl->offline.
--

Adding this option makes it easier to implement the corresponding
feature in gpgme.

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

sm/gpgsm.h

@@ -201,6 +201,7 @@ struct server_control_s
   int validation_model; /* 0 := standard model (shell),
                            1 := chain model,
                            2 := STEED model. */
+  int offline;        /* If true gpgsm won't do any network access.  */
 };