player: send chunk tag to audio device

If a chunk contains a tag, send it to the audio output device.  Few
output plugins support this, e.g. shout has support for sending tags.

src/player_thread.c

@@ -213,6 +213,9 @@ playChunk(struct music_chunk *chunk, const struct audio_format *format,
 	pc.elapsedTime = chunk->times;
 	pc.bitRate = chunk->bit_rate;
 
+	if (chunk->tag != NULL)
+		sendMetadataToAudioDevice(chunk->tag);
+
 	pcm_volume(chunk->data, chunk->length,
 		   format, pc.softwareVolume);