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/osgSim/LightPointNode

@@ -82,6 +82,8 @@ class OSGSIM_EXPORT LightPointNode : public osg::Node
 
         osgSim::LightPointSystem* getLightPointSystem() { return _lightSystem.get(); }
 
+        virtual osg::BoundingSphere computeBound() const;
+
     protected:
 
         ~LightPointNode() {}
@@ -90,8 +92,6 @@ class OSGSIM_EXPORT LightPointNode : public osg::Node
         // view frustum check. 
         mutable osg::BoundingBox _bbox;
 
-        virtual bool computeBound() const;
-
         LightPointList  _lightPointList;
 
         float _minPixelSize;