Point debuggerd at the interesting thread.

There are a couple of situations (spin-on-suspend, HeapWorker wedged)
where the current thread's native stack is much less interesting than one
of the others.  This change will cause a couple of signals to be thrown
at the "interesting" thread in an attempt to get more useful information
out of debuggerd in these cases.

For bug 2517042.

Change-Id: Ib8c0e0ef93f07b7114e5f4638a907a0f7802bdc0
3 files changed