select returns with -1.
* tools.texi (gpg-connect-agent): New.
* app-openpgp.c (get_one_do): Never try to get a non cacheable
object from the cache.
(get_one_do): Add new arg to return an error code. Changed all
callers.
(do_getattr): Let it return a proper error code.
* app.c (select_application): Return an error code and the
application context in an new arg.
* command.c (open_card): Adjusted for that. Don't use the
fallback if no card is present. Return an error if the card has
been removed without a reset.
(do_reset, cmd_serialno): Clear that error flag.
(TEST_CARD_REMOVAL): New. Use it with all command handlers.
* scdaemon.c (ticker_thread): Termintate if a shutdown is pending.
* apdu.c: Added some PCSC error codes.
(pcsc_error_to_sw): New.
(reset_pcsc_reader, pcsc_get_status, pcsc_send_apdu)
(open_pcsc_reader): Do proper error code mapping.
* gpg-connect-agent.c: New.
* Makefile.am: Add it.
