void htb_charge_class (struct htb_sched * q, struct htb_class * cl, int level, int bytes);
Routine assumes that packet ``bytes'' long was dequeued from leaf cl borrowing from ``level''. It accounts bytes to ceil leaky bucket for leaf and all ancestors and to rate bucket for ancestors at levels ``level'' and higher. It also handles possible change of mode resulting from the update. Note that mode can also increase here (MAY_BORROW to CAN_SEND) because we can use more precise clock that event queue here. In such case we remove class from event queue first.