kernel - Filter out unknown errors for select(2) and poll(2)

kernel - Filter out unknown errors for select(2) and poll(2)

* select/poll have very limited error management, silently ignore anything they
  cannot handle (this brings us closer in line with the previous
  implementation).

* Add a couple of kern.nseldebug kprintf's

* Increment the kqueue serial by the number of descriptors for both select
  and poll.