From Aurélien Chatelain, "adds support for
* quad primitives
* face definition with the "vertex_index" label (previously only "vertex_indices" was supported)
* replaces normal computation by the SmoothingVisitor to avoid code duplication
"

Submitted by Marc Helbling.


git-svn-id: http://svn.openscenegraph.org/osg/OpenSceneGraph/trunk@14640 16af8721-9629-0410-8352-f15c8da7e697