faster max slide speed (max 4 semitones per tick, was 1 semitone per tick)

tracker_engine/tracker_engine.c

@@ -373,12 +373,12 @@ void tracker_engine_advance_channel(TrackerEngine* tracker_engine, uint8_t chan)
         if(te_channel->slide_speed != 0) {
             if(te_channel->target_note > te_channel->note) {
                 te_channel->note +=
-                    my_min(te_channel->slide_speed, te_channel->target_note - te_channel->note);
+                    my_min(te_channel->slide_speed * 4, te_channel->target_note - te_channel->note);
             }
 
             else if(te_channel->target_note < te_channel->note) {
                 te_channel->note -=
-                    my_min(te_channel->slide_speed, te_channel->note - te_channel->target_note);
+                    my_min(te_channel->slide_speed * 4, te_channel->note - te_channel->target_note);
             }
         }