to compute the required matrix rather than using the NodePath provided by the NodeVistor. This is required
as in osg::computeLocalToWorld() usage case the NodeVisitor pointer is NULL, so the correct matrix isn't possible to compute.
git-svn-id: http://svn.openscenegraph.org/osg/OpenSceneGraph/trunk@14828 16af8721-9629-0410-8352-f15c8da7e697