* command.c (start_command_handler): Init it here.
* gpg-agent.c (agent_init_default_ctrl): and here.
* call-scd.c: Add the CTRL arg to all functions calling start_scd
and pass it to start_scd. Changed all callers
(start_scd): Keep track of the current active connection.
(agent_reset_scd): New.
* command.c (start_command_handler): Call it here.
* learncard.c (agent_handle_learn): Add arg CTRL; changed caller.
(send_cert_back): Ditto.