made removeExpiredSubgraphs virtual.
made removeExpiredSubgraphs virtual.


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