Add preliminary audio processing

- Mixing still isn't implemented, but the audio system should be able
   to start up, and mix at least once audio line for the time being.
   Will have to write some test audio sources to verify things are
   working properly, and build the rest of the output functionality.

libobs/obs.c

@@ -355,14 +355,11 @@ bool obs_reset_video(struct obs_video_info *ovi)
 
 bool obs_reset_audio(struct audio_info *ai)
 {
-	/*obs_free_audio();
+	obs_free_audio();
 	if(!ai)
 		return true;
 
-	return obs_init_audio(ai);*/
-
-	/* TODO */
-	return true;
+	return obs_init_audio(ai);
 }
 
 bool obs_get_video_info(struct obs_video_info *ovi)