* scd/app.c (lock_table): Remove LAST_APP field.
(lock_reader, app_dump_state, application_notify_card_reset)
(release_application): Follow the change.
(check_conflict): New.
(check_application_conflict): Lock the slot and call check_conflict.
(select_application): Call check_conflict and not use LAST_APP.
--
We don't need LAST_APP field but just keep the application context by
APP field. Since we have a reference counter, it is possible if we
can deallocate or not.
(backport of commit 9639af5f16a7ed908cbce2415330b9fcd88edc90)