message: Make packed overload of onMove the primary
  Unpacked overload delegates to packed overload.
diff: @@ -65,8 +65,8 @@ protected:
  * \param dX Difference in X Position.
  * \param dY Difference in Y Position.
  */
  - virtual void positionChanged(int dX, int dY) { mPositionChanged({dX, dY}); }
  - void positionChanged(NAS2D::Vector<int> displacement) { positionChanged(displacement.x, displacement.y); }
  + virtual void positionChanged(int dX, int dY) { positionChanged({dX, dY}); }
  + void positionChanged(NAS2D::Vector<int> displacement) { mPositionChanged(displacement); }
  virtual void visibilityChanged(bool /*visible*/) {}
  