Added a DeleteHandler into osg::Referenced so that it can delete objects

via a seperate delete handler.  Useful for making unref()/ref() thread safe if
the users needs to address this issue.

src/osg/Object.cpp

@@ -1,28 +1,12 @@
 #include <osg/Object>
-#include <osg/Notify>
-#include <typeinfo>
 
-using namespace osg;
-
-#ifdef OSG_COMPILE_UNIT_TESTS
-int Referenced::_createdCount = 0;
-int Referenced::_deletedCount = 0;
-#endif
-
-Referenced::~Referenced()
+namespace osg
 {
-    if (_refCount>0)
-    {
-        notify(WARN)<<"Warning: deleting still referenced object "<<this<<" of type '"<<typeid(this).name()<<"'"<<std::endl;
-        notify(WARN)<<"         the final reference count was "<<_refCount<<", memory corruption possible."<<std::endl;
-    }
-#ifdef OSG_COMPILE_UNIT_TESTS
-    _deletedCount ++;
-#endif
-}
-
 
 Object::Object(const Object& obj,const CopyOp& copyop): 
     Referenced(),
     _dataVariance(obj._dataVariance),
     _userData(copyop(obj._userData.get())) {}
+
+
+}; // end of namespace osg