Well the trick is that we can't use that function directly if it is only for level 19. We need to wrap it into subclass like http://www.androiddesignpatterns.com/2012/06/designing-for-backwards-compatibility.html or https://github.com/osmandapp/Osmand/blob/master/OsmAnd/src/net/osmand/plus/views/MultiTouchSupport.java#L67 
TargetSdk doesn't solve backward compatibility issue. It would be good to try without target sdk, usually changing target sdk gives unexpected surprises with UI (dialog changing style and so on).

I think we can update target-sdk later after release, but I have the feeling that this patch will be needed for this release.