SilcTask
    silc_schedule_task_add_timeout(SilcSchedule schedule,
                                   SilcTaskCallback callback, void *context,
                                   long seconds, long useconds);

    Add timeout task to scheduler.  The `callback' will be called once
    the specified timeout has elapsed.  The task will be removed from the
    scheduler automatically once the task expires.  The event returned
    to the `callback' is SILC_TASK_EXPIRE.  A task added with zero (0)
    timeout will be executed immediately next time tasks are scheduled.