audioqueue: don't use the main CFRunLoop for the (empty) data callback, but...

audioqueue: don't use the main CFRunLoop for the (empty) data callback, but one of AudioQueue's internal threads

Otherwise, we will encounter delays of up to 10 secs when stopping the AudioQueue

modules/audio_output/audioqueue.c

@@ -97,7 +97,7 @@ static int Start(audio_output_t *p_aout, audio_sample_format_t *restrict fmt)
     status = AudioQueueNewOutput(&deviceFormat,         // Format
                                  AudioQueueCallback,    // Callback
                                  NULL,                  // User data, passed to the callback
-                                 CFRunLoopGetMain(),    // RunLoop
+                                 NULL,                  // RunLoop
                                  kCFRunLoopCommonModes, // RunLoop mode
                                  0,                     // Flags ; must be zero (per documentation)...
                                  &(p_sys->audioQueue)); // Output