* tools/gpg-auth.c (my_strusage): Fix usage string.
(main): Use gpg-agent to get scdaemon socket.
(authenticate): Return GPG_ERR_NOT_FOUND when no success.
(ga_scd_connect): Use DBG_IPC.
(inq_needpin): Change API for getpin.
(put_second_field_cb): New, to get the second field.
(scd_get_pubkey): Use put_second_field_cb.
(ga_filter_by_authorized_keys): Put NULL at the PREV->next.
(getpin): Flush the standard output.
Include the last terminating NUL.
Return the length.