- Fixed a few bugs with ringbuffer, and some cleanup.

- Reworked audio system to use semaphores instead of events for waiting.
  Should fix rare issues where the XAudio2 driver would run out of buffers
  even though it was supposed to be guarded against that.

src/xenia/apu/xaudio2/xaudio2_audio_system.h

@@ -24,7 +24,7 @@ class XAudio2AudioSystem : public AudioSystem {
   XAudio2AudioSystem(Emulator* emulator);
   virtual ~XAudio2AudioSystem();
 
-  virtual X_RESULT CreateDriver(size_t index, HANDLE wait,
+  virtual X_RESULT CreateDriver(size_t index, HANDLE semaphore,
                                 AudioDriver** out_driver);
   virtual void DestroyDriver(AudioDriver* driver);