fixed compilation problem (frame.h not included)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@9408 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

contrib/include/wx/xml/xmlres.h

@@ -30,6 +30,7 @@ class WXDLLEXPORT wxMenuBar;
 class WXDLLEXPORT wxDialog;
 class WXDLLEXPORT wxPanel;
 class WXDLLEXPORT wxWindow;
+class WXDLLEXPORT wxFrame;
 class WXDLLEXPORT wxToolBar;
 
 class WXDLLEXPORT wxXmlResourceHandler;