* scd/app.c: Include membuf.h.
(app_switch_current_card): New.
(send_card_and_app_list): Factor code out to ...
(send_serialno_and_app_status): new.
(app_send_card_list): New.
(app_send_active_apps): New.
(app_switch_active_app): New.
* scd/command.c (cmd_switchcard): New.
(cmd_switchapp): New.
(register_commands): Register new commands.
(cmd_getinfo): New sub-commands "active_apps" and "all_active_apps".