This fix reverses the vertex order and sets up proper OpenGL facing. I didn't notice this problem until I started using the plug-in in my own code (osgviewer seems to not enable backface culling)."
merged from svn/trunk using:
svn merge -r 10092:10093 http://www.openscenegraph.org/svn/osg/OpenSceneGraph/trunk/src/osgPlugins/mdl/