Added #include <osg/ref_ptr> so that it will compile properly regardless of include order.
Added #include <osg/ref_ptr> so that it will compile properly regardless
of include order.


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