Test: sched_jitter
===================
This test measures scheduling jitter w/ realtime processes.

It spawns a realtime thread that repeatedly times how long it takes to do a
fixed amount of work.  It then prints out the maximum jitter seen (longest
execution time - the shortest execution time).

It also spawns off a realtime thread of higher priority that simply wakes up
and goes back to sleep.  This tries to measure how much overhead the scheduler
adds in switching quickly to another task and back.
