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

include/wx/gtk/clipbrd.h

@@ -18,7 +18,7 @@ class WXDLLIMPEXP_CORE wxClipboard : public wxClipboardBase
 {
 public:
     wxClipboard();
-    ~wxClipboard();
+    virtual ~wxClipboard();
 
     // open the clipboard before SetData() and GetData()
     virtual bool Open();