Made the more of the OSG's referenced object desctructors protected to ensure

that they arn't created on the stack inappropriately.

Split the implemention of Matrix up so that it is a simple no referenced counted
class and can be safefly created on the stack.  To support referenced counting a
seperate subclass now exists, this is RefMatrix which inherits from both Matrix and
Object.

src/osgSim/LightPointNode.cpp

@@ -113,7 +113,7 @@ void LightPointNode::traverse(osg::NodeVisitor& nv)
     {
     
         osg::Matrix matrix = cv->getModelViewMatrix();
-        osg::Matrix& projection = cv->getProjectionMatrix();
+        osg::RefMatrix& projection = cv->getProjectionMatrix();
         osgUtil::RenderGraph* rg = cv->getCurrentRenderGraph();
 
         if (rg->leaves_empty())