Added --mouse option to enable mouse tracking, and fixed bug in assumption that nv is not null.
Added --mouse option to enable mouse tracking, and fixed bug in assumption
that nv is not null.


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