* scd/apdu.c (pcsc): New variable.
(struct reader_table_s): Remove pcsc.context from member.
(pcsc_get_status, connect_pcsc_card): Use pcsc.context.
(close_pcsc_reader): Release pcsc.context here with reference count.
(pcsc_init): New.
(open_pcsc_reader): Don't call pcsc_establish_context here.  Call
close_pcsc_reader instead of pcsc_release_context.
(apdu_open_reader): Call pcsc_init if needed.
(apdu_init): Initialize pcsc.count and pcsc.context.