Added osg::Capability and Cabibilityi base classes to wrap up glEnable/glDisable + glEnablei/glDisablei functionality, with osg::Enablei and osg::Disablei concrete implementations.


git-svn-id: http://svn.openscenegraph.org/osg/OpenSceneGraph/trunk@14564 16af8721-9629-0410-8352-f15c8da7e697