Added command line option --overlay to turn on the use of an OverlayNode.
Added command line option --overlay to turn on the use of an OverlayNode.


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