implement proper bitmap copying

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@42882 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk1/bitmap.h

@@ -135,6 +135,9 @@ public:
 protected:
     bool CreateFromImage(const wxImage& image, int depth);
 
+    virtual wxObjectRefData *CreateRefData() const;
+    virtual wxObjectRefData *CloneRefData(const wxObjectRefData *data) const;
+
 private:
     // to be called from CreateFromImage only!
     bool CreateFromImageAsBitmap(const wxImage& image);