Removed some warnings in widgets sample

Reduced some flicker in wxNotebook when using
XP controls


git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@22413 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/notebook.h

@@ -148,6 +148,8 @@ protected:
   // set the size of the given page to fit in the notebook
   void AdjustPageSize(wxNotebookPage *page);
 
+  // override WndProc
+  virtual long MSWWindowProc(WXUINT nMsg, WXWPARAM wParam, WXLPARAM lParam);
 
   // the current selection (-1 if none)
   int m_nSelection;