Added CameraNode::releaseGLObejcts() to help in clean up, and changed the

ordering in SceneView::flushDeleteGLObjects() so that fbo's are deleted
before any texture objects they use are deleted.

src/osgProducer/OsgCameraGroup.cpp

@@ -741,6 +741,7 @@ void OsgCameraGroup::cleanup_frame()
         ++itr)
     {
         (*itr)->getSceneView()->releaseAllGLObjects();
+        (*itr)->getSceneView()->setRenderStage(0);
         (*itr)->setCleanUpOnNextFrame(true);
     }