Added osg::Grid shape class, and added an example of its use into the

hang glide demo.

src/osgDB/Registry.cpp

@@ -70,7 +70,10 @@ Registry::Registry()
 
     addFileExtensionAlias("tif",  "tiff");
 
-    addFileExtensionAlias("geo",  "lwo");
+    // remove geo to lwo alias as the new Carbon Graphics GEO format
+    // also uses the .geo. It is still possible to load light wave .geo
+    // files via loading the lwo plugin explicitly and then doing a readNodeFile.
+    //addFileExtensionAlias("geo",  "lwo");
     addFileExtensionAlias("lw",   "lwo");
 
     addFileExtensionAlias("wrl",   "iv");