update debug message for MIDI control events

src/midi.cpp

@@ -82,7 +82,7 @@ midiProcess(const snd_seq_event_t* ev)
 	}
 	else if(ev->type == SND_SEQ_EVENT_CONTROLLER)
 	{
-		printf("[%d] Control:  %2x val(%2x)\n",
+		printf("[%d] Control:  0x%2x val(%2x)\n",
 				ev->time.tick,
 				ev->data.control.param,
 				ev->data.control.value);