Began work on providing support for threading camera cull traversals in parallel with

the previous frames draw traversal.  Changes range from osg::State, through osgUtil::RenderBin, through to osgViewer

src/osg/Drawable.cpp

@@ -246,6 +246,8 @@ void Drawable::flushDeletedVertexBufferObjects(unsigned int contextID,double /*c
 
 Drawable::Drawable()
 {
+    setDataVariance(osg::Object::STATIC);
+
     _boundingBoxComputed = false;
 
     // Note, if your are defining a subclass from drawable which is