* agent/agent.h (CACHE_MODE_PIN): New.
* agent/cache.c (housekeeping): Special handling of new new mode.
(agent_flush_cache): Ditto.  Add arg 'pincache_only' and change
caller.
(agent_put_cache): Support new mode.
(agent_get_cache): Ditto.
* agent/call-scd.c (wait_child_thread): Flush the entire PIN cache.
(start_scd): Ditto.
(agent_card_killscd): Ditto.
(handle_pincache_put): New.  Uses a dummy encryption key for now.
(pincache_put_cb): New.
(inq_needpin): Prepare for PINCACHE_GET inquiry.
(learn_status_cb): Handle the PINENTRY_PUT status line.
(get_serialno_cb): Ditto
(agent_card_pksign): Ditto.
(padding_info_cb): Ditto.
(agent_card_readcert): Ditto.
(agent_card_readkey): Ditto.
(agent_card_writekey): Ditto.
(card_getattr_cb): Ditto.
(card_cardlist_cb): Ditto.
(card_keyinfo_cb): Ditto.
(pass_status_thru): Ditto.