scd: Support "acknowledge button" feature.
* scd/apdu.c (set_prompt_cb): New member function. (set_prompt_cb_ccid_reader): New function. (open_ccid_reader): Initialize with set_prompt_cb_ccid_reader. (apdu_set_prompt_cb): New. * scd/app.c (lock_app, unlock_app): Add call to apdu_set_prompt_cb. * ccid-driver.c (ccid_set_prompt_cb): New. (bulk_in): Call ->prompt_cb when timer extension. * scd/command.c (popup_prompt): New.
- Signed-off-by: NIIBE Yutaka <gniibe@fsij.org>