Added new Node/Drawable::s/getInitialBound and Node/Drawable::s/getComputeBoundCallback

methods and reimplement computeBound so that it passes back a bounding volume rather
than modifying the local one.

include/osg/LightSource

@@ -72,12 +72,12 @@ class OSG_EXPORT LightSource : public Group
         /** Set up the local StateSet. */
         void setLocalStateSetModes(StateAttribute::GLModeValue value = StateAttribute::ON);
 
+        virtual BoundingSphere computeBound() const;
+
     protected:
 
         virtual ~LightSource();
 
-        virtual bool computeBound() const;
-
         StateAttribute::GLModeValue     _value;
         ref_ptr<Light>                  _light;