* agent/call-pinentry.c (agent_get_confirmation): Add call of
pinentry_loopback_confirm.
(agent_popup_message_start): Likewise.
(agent_popup_message_stop): Return if it's loopback mode.
* agent/command.c (pinentry_loopback_confirm): New.
* g10/call-agent.c (default_inq_cb): Support "CONFIRM" inquery
when PINENTRY_MODE_LOOPBACK mode.
(confirm_status_cb): New.
(agent_delete_key): Supply confirm_status_cb to set the description
string for confirmation.

    [gpg]                            [gpg-agent]
            --- CMD: PKDECRYPT -->
            <-- STATUS: SETDESC "..."
            <-- STATUS: SETOK "..."
            <-- STATUS: SETNOTOK "..."
            <-- INQUERY: CONFIRM 0/1 (0 for display, 1 for user query)
	    --- INQUERY-result: -->
	    <-- RESULT: ...