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.

include/osg/AnimationPath

@@ -182,6 +182,11 @@ class SG_EXPORT AnimationPathCallback : public NodeCallback
         double                  _timeMultiplier;
         double                  _firstTime;
         mutable double          _animationTime;
+
+    protected:
+    
+        ~AnimationPathCallback(){}
+
 };
 
 }