Run IP input and forwarding with shared netlock. Also distribute

Run IP input and forwarding with shared netlock.  Also distribute
packets from the interface receive rings into multiple net task
queues.
Note that we still have only one softnet task.  So there will be
no concurrency yet, but we can notice wrong exclusive lock assertions.
Soon the final step will be to increase the NET_TASKQ define.
lots of testing Hrvoje Popovski; OK sashan@