Reduce VM aborts during high CPU stress.

Reduce VM aborts during high CPU stress.

The VM has some timeouts that are meant to kill the current process if
something gets stuck (e.g. a thread grabs a lock and then manages to die
while the rest of the process continues on).  These were tripping a
little too easily during some high-load situations.

This changes the order of operations so that we now unlock the "thread
suspend" lock before sending a wakeup broadcast to the condition variable
that threads sleep on.  This should make it less likely for a thread to
be running for an extended period while the lock is held.  (Relates to
internal bug 1664687.)

This also wraps a couple of things (pthread_create, dlopen) with a state
change to VMWAIT.  During high load situations these can take a while to
complete, and we would (with the K-Means Visualizer load generator
running) very occasionally time out.

Augmented the debug output in a couple of minor ways.  Updated comments.