kernel - Add batch heuristic to scheduler and refactor some of the code 1/2

kernel - Add batch heuristic to scheduler and refactor some of the code 1/2

* Split the dynamic priority mechanism into two stages:

* Stage 1 is the normal dynamic priority mechanism which reacts very quickly
  to cpu hogging vs idle / not hogging.

* Stage 2 is a long-term (30-second) batch operations detector which de-tunes
  the estcpu calculation based on how long the process has been acting
  batch-like or non-batch-like.  estcpu is detuned up to 50% for processes
  considered to be fully interactive.

* Newly forked processes are placed two queue slots higher (less desireable)
  than their parent in stage 1.  If they aren't batch they will quickly
  recover.

* Newly forked processes are given a batch heuristic value that is mid-range
  for stage 2 and must prove themselves one way or the other.

* 'ps -o batch -axl' can be used to see the batch heuristic.  ps will display
  it as a value between 0 and 11 for the moment.

  The idea here is for something like firefox and the X server to remain
  interactive even if they use a lot of cpu, while something like a parallel
  buildworld winds up remaining batch-like because the core processes are
  cpu-bound.