Added back in the call to drawPreRenderStages() as this shouldn't interfere

with the stereo code in SceneView as RenderStage should automatically only
allow themselves to be draw on per frame.

src/osgUtil/RenderStage.cpp

@@ -118,7 +118,7 @@ void RenderStage::draw(osg::State& state,RenderLeaf*& previous)
 
     // note, SceneView does call to drawPreRenderStages explicitly
     // so there is no need to call it here.
-    //drawPreRenderStages(state,previous);
+    drawPreRenderStages(state,previous);
 
     RenderBin::draw(state,previous);