scd: Add debug option for reader function calls.
* scd/scdaemon.h (DBG_READER_VALUE, DBG_READER): New. * scd/apdu.c (apdu_open_reader, apdu_close_reader) (apdu_shutdown_reader, apdu_connect, apdu_disconnect) (apdu_reset, apdu_get_atr, apdu_get_status): Add debug code. (apdu_activate): Remove this unused function.