scd: Fix use case of PC/SC.

scd: Fix use case of PC/SC.

* scd/apdu.c (apdu_open_reader): Add an argument APP_EMPTY.
When CCID driver fails to open, try PC/SC if APP is nothing.
* scd/app.c (select_application): Supply arg if APP is nothing.

--

After scanning available card readers by CCID driver, scdaemon should
try PC/SC service if no APP is registered yet.  Also, when the slot
is allocated for PC/SC (ccid.handle==NULL), it should not call
ccid_compare_BAI, otherwise scdaemon crashes.

Debian-bug-id: 852702, 854005, 854595, 854616

Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>
Gbp-Pq: Name 0029-scd-Fix-use-case-of-PC-SC.patch