Yet more scheduler work. Revamp the batch detection heuristic and fix a few
things here and there. Test the algorithm against buildworlds, mozilla,
gnome-terminal, and pine all running at once.
* Fix a bug in how I handle p_slptime.
* Move the ++p_cptime out of usched_bsd4 and into kern_clock.c.
* Redo the batch heuristic, boost the cost of doing a fork, and
slowly decrement p_origcpu to compensate for long-running
processes.
* Use an instantanious load instead of a time-averaged load in the
decay calculation.
TODO: the SMP support will be virtually identical across all schedulers
and should probably be abstracted out of usched_*.c.