Backed out changeset cec31de4e126

This was meant to migrate CoreAudio onto the same SDL_RunAudio() path that
most other audio drivers are on, but it introduced a bug because it doesn't
deal with dropped audio buffers...and fixing that properly just introduces
latency.

I might revisit this later, perhaps by reworking SDL_RunAudio to allow for
this sort of API better, or redesigning the whole subsystem or something, I
don't know. I'm not super-thrilled that this has to exist outside of the usual
codepaths, though.

Fixes Bugzilla #4481.

src/audio/coreaudio/SDL_coreaudio.h

@@ -45,14 +45,16 @@
 
 struct SDL_PrivateAudioData
 {
+    SDL_Thread *thread;
     AudioQueueRef audioQueue;
-    int numAudioBuffers;
     AudioQueueBufferRef *audioBuffer;
     void *buffer;
+    UInt32 bufferOffset;
     UInt32 bufferSize;
     AudioStreamBasicDescription strdesc;
-    SDL_bool refill;
-    SDL_AudioStream *capturestream;
+    SDL_sem *ready_semaphore;
+    char *thread_error;
+    SDL_atomic_t shutdown;
 #if MACOSX_COREAUDIO
     AudioDeviceID deviceID;
 #else