Added a check to the destructor of Referenced so that it detects referenced

objects that are deleted whilest still having a positive _refCount, such
as when a object has been deleted on the stack, yet other references still
exist for it.  Have put the desctructor implementation in Object.cpp to
avoid adding yet another file with only a couple of lines of code in.

src/osg/Object.cpp

@@ -1,6 +1,18 @@
 #include <osg/Object>
+#include <osg/Notify>
+#include <typeinfo>
 
 using namespace osg;
 
+Referenced::~Referenced()
+{
+    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;
+    }
+}
+
+
 Object::Object(const Object&,const CopyOp&): 
     Referenced() {}