tune forkjoinpool to now call PR_Now() quite so often
Make exec correspond to *just ion execution*, which is really what
we want to be optimizing for
Just measure ion time for Exec measurement
Replace calls to PR_Now with busy loops, in an effort to improve
perf at higher # of threads. Didn't work.
separate out main from worker thread in profiling
Instrument compile time
Add internal call to reset fork join counters so we are only measuring steady state
switch to use atomic counters for tracking active threads