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/osgDB/Registry

@@ -35,15 +35,12 @@ typedef std::deque<std::string> FilePathList;
     The RegisterReaderWriterProxy can be used to automatically
     register at runtime a reader/writer with the Registry.
 */
-class OSGDB_EXPORT Registry
+class OSGDB_EXPORT Registry : public osg::Referenced
 {
     public:
 
         static Registry* instance();
 
-        ~Registry();
-
-
         /** read the command line string list, removing any matched control sequences.*/
         void readCommandLine(std::vector<std::string>& commandLine);
 
@@ -142,7 +139,9 @@ class OSGDB_EXPORT Registry
         static void convertStringPathIntoFilePathList(const std::string& paths,FilePathList& filepath);
 
 
-    private:
+    protected:
+
+        virtual ~Registry();
 
         typedef std::map<std::string,osg::ref_ptr<DotOsgWrapper> >  DotOsgWrapperMap;
         typedef std::vector<osg::ref_ptr<ReaderWriter> >            ReaderWriterList;