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/cocoa/mdi.h

@@ -156,7 +156,7 @@ class wxMDIClientWindow: public wxWindow
 public:
     wxMDIClientWindow();
     wxMDIClientWindow( wxMDIParentFrame *parent, long style = 0 );
-    ~wxMDIClientWindow();
+    virtual ~wxMDIClientWindow();
     virtual bool CreateClient( wxMDIParentFrame *parent, long style = 0 );
 };