Updates to data sources.

  * ma_data_source_read_pcm_frames and ma_data_source_seek_pcm_frames
    now return a result code and output the frames read/seeked as an
    output parameter.
  * These return MA_AT_END if the end of the data source has been
    reached. This should never be returned if the loop parameter is set
    to true.

examples/simple_looping.c

@@ -23,7 +23,7 @@ void data_callback(ma_device* pDevice, void* pOutput, const void* pInput, ma_uin
     A decoder is a data source which means you can seemlessly plug it into the ma_data_source API. We can therefore take advantage
     of the "loop" parameter of ma_data_source_read_pcm_frames() to handle looping for us.
     */
-    ma_data_source_read_pcm_frames(pDecoder, pOutput, frameCount, isLooping);
+    ma_data_source_read_pcm_frames(pDecoder, pOutput, frameCount, NULL, isLooping);
 
     (void)pInput;
 }