Fixed two threading problems on the OpenAL backend that caused warnings and
intermittent crashes on application exit.
1. The change to StreamUpdater.cpp fixes the case where the Thread base class
destructor gets called before the tread has a chance to exit. This resulted in
a warning from the base class and, at least in our application, intermittent
crashes on exit when these destructors were invoked.
2. The change to FileStreamUpdater.cpp fixes a case where the thread can never
exit once EOF is reached in non-looping mode (was stuck in inner loop).