From Ruben, added support for nested update and cull callbacks.
From Ruben, added support for nested update and cull callbacks.


jtorresfabra/osg,artoolkit/osg,tomasthoresen/osg,marchelbling/osg,scrawl/osg,scrawl/osg,tomasthoresen/osg,artoolkit/osg,openscenegraph/osg,artoolkit/osg,openscenegraph/osg,scrawl/osg,marchelbling/osg,openscenegraph/osg,openscenegraph/osg,scrawl/osg,marchelbling/osg,jtorresfabra/osg,jtorresfabra/osg,artoolkit/osg,jtorresfabra/osg,marchelbling/osg,tomasthoresen/osg,tomasthoresen/osg