Moved GL2Extensions functionality into the include/osg/GLExtensions header and new GLExtensions object.

Moved the #defines into new include/osg/GLDefines
Converted all GL2Extensions usage to GLExtensions usage


git-svn-id: http://svn.openscenegraph.org/osg/OpenSceneGraph/trunk@14593 16af8721-9629-0410-8352-f15c8da7e697

src/osgFX/SpecularHighlights.cpp

@@ -114,7 +114,7 @@ namespace
         {
             if (!Technique::validate(state)) return false;
 
-            osg::GL2Extensions *ext = state.get<osg::GL2Extensions>();
+            osg::GLExtensions *ext = state.get<osg::GLExtensions>();
             return ext ?  ext->isCubeMapSupported : false;
         }