BGE: Occlusion culling and other performance improvements.

Added occlusion culling capability in the BGE. 
More info: http://wiki.blender.org/index.php/Dev:Ref/Release_Notes/2.49/Game_Engine#BGE_Scenegraph_improvement
MSVC, scons, cmake, Makefile updated.

Other minor performance improvements:
- The rasterizer was computing the openGL model matrix of the objects too many times
- DBVT view frustrum culling was not properly culling behind the near plane:
  Large objects behind the camera were sent to the GPU
- Remove all references to mesh split/join feature as it is not yet functional

source/gameengine/VideoTexture/ImageRender.cpp

@@ -249,7 +249,7 @@ void ImageRender::Render()
     // restore the stereo mode now that the matrix is computed
     m_rasterizer->SetStereoMode(stereomode);
 
-    // do not update the mesh, we don't want to do it more than once per frame
+    // do not update the mesh transform, we don't want to do it more than once per frame
     //m_scene->UpdateMeshTransformations();
 
 	m_scene->CalculateVisibleMeshes(m_rasterizer,m_camera);