message: Add Vector overload for Control::positionChanged
diff: @@ -77,6 +77,7 @@ protected:
  * \param dY Difference in Y Position.
  */
  virtual void positionChanged(float dX, float dY) { mPositionChanged(dX, dY); }
  + void positionChanged(NAS2D::Vector<float> displacement) { positionChanged(displacement.x, displacement.y); }
  virtual void visibilityChanged(bool /*visible*/) {}
  