The main thread is somewhat special in D--it doesn't actually terminate until
all other threads have terminated. And because the "OwnerTerminated" message
is sent in a static dtor, the ordering is wrong for having spawned threads
receive this message. I'll leave it up to Andrei to decide whether this is
correct behavior or if the OwnerTerminated message should be sent when D main()
exits (I'm leaning towards this latter behavior myself). If a change is
necessary I'll have to add a stack for onMainExit callbacks to be executed in
druntime.
