fixed wxBitmapButton to use focus and hover bitmaps correctly

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@52007 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/bmpbuttn.h

@@ -68,6 +68,8 @@ protected:
     void Init();
 
 private:
+    void OnFocusChange(wxFocusEvent& event);
+
     DECLARE_DYNAMIC_CLASS(wxBitmapButton)
 };