Add suspend count to thread implementation.
Increment suspend count on suspend and decrement on resume.
Wait on suspend count to be decremented to 0.
Return suspend count on suspend and on resume before incr/decr.
Fix naming of resume suspend count to make clear that suspend count is
before incr/decr.
Add test.
Test Manual Reset and Synchronization timers single threaded.
Test Cancelling timers.
Test WaitMultiple.
Ignore real-time event 35 in .gdbinit which is used to signal timer.
Callbacks don't seem to be called so testing them is difficult.
Remove atomic boolean in fence. Variable signaled_ is already protected
by mutex.
Remove wait loop with single predicate wait protected with mutex.
Add Fence Signal and Wait tests
Test signaling without waiting.
Test signaling before waiting.
Test signaling twice before waiting.
Test synchronizing threads with fence.
Few REQUIRES were used to test as there are no return codes.
A failing test may hang indefinitely or cause a segfault which would still
register as a fail.
