BGE performance:

- Vast performance increase when removing scene containing large number of 
  objects: the sensor/controller map was updated for each deleted object, 
  causing massive slow down when the number of objects was large (O(n^2)).
- Use reference when scanning the sensor map => avoid useless copy.
- Remove dynamically the object bounding box from the DBVT when the object
  is invisible => faster culling.

source/gameengine/Ketsji/KX_GameObject.cpp

@@ -628,6 +628,8 @@ KX_GameObject::SetVisible(
 {
 	if (GetSGNode()) {
 		m_bVisible = v;
+		if (m_pGraphicController)
+			m_pGraphicController->Activate(m_bVisible);
 		if (recursive)
 			setVisible_recursive(GetSGNode(), v);
 	}