Restore lost TICK case

See the comments on https://github.com/thestk/rtmidi/commit/403414019715d56e990da67b9268dee0ecf03c50

RtMidi.cpp

@@ -1212,7 +1212,7 @@ extern "C" void *alsaMidiHandler( void *ptr )
       if ( !( data->ignoreFlags & 0x02 ) ) doDecode = true;
       break;
 
-    case SND_SEQ_EVENT_CLOCK: // MIDI timing tick
+    case SND_SEQ_EVENT_TICK: // MIDI timing tick
       if ( !( data->ignoreFlags & 0x02 ) ) doDecode = true;
       break;