mark all dtors which are virtual because base class dtor is virtual explicitly virtual themselves

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@41020 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/gtk/cursor.cpp

@@ -29,7 +29,7 @@ class wxCursorRefData: public wxObjectRefData
   public:
 
     wxCursorRefData();
-    ~wxCursorRefData();
+    virtual ~wxCursorRefData();
 
     GdkCursor *m_cursor;
 };