kernel - kqueue select support

kernel - kqueue select support

* Fix bug in kevent timeout handling.  Only go to non-blocking once
  (*res) is non-zero.

* Use stack-declared kfd_set structures for select operations on
  64 or fewer descriptors.

* Refactor the select_copyin() loop.

* Fix bug in serial number decoding in the select_copyout() loop.

* Do not use EV_CLEAR, this can cause temporary EOF conditions to
  reset improperly.  Do not use EV_ONESHOT either.  Leave the event
  in the kqueue, it will speed things up when select() is called in
  a loop (the events will already exist).

* Implement ptckqfilter ... implement kqfilter functions for pty's and
  ptc's instead of using the tty kqfilter functions which do not work
  properly for ptc control terminals.

* Change getbits/putbits from macros to inline functions.