replace m_insertCallback with a virtual function, contrary to the old comments a virtual works just fine

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@55354 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/notebook.h

@@ -8,8 +8,8 @@
 // Licence:     wxWindows licence
 /////////////////////////////////////////////////////////////////////////////
 
-#ifndef __GTKNOTEBOOKH__
-#define __GTKNOTEBOOKH__
+#ifndef _WX_GTKNOTEBOOK_H_
+#define _WX_GTKNOTEBOOK_H_
 
 //-----------------------------------------------------------------------------
 // internal class
@@ -135,9 +135,10 @@ private:
     // the padding set by SetPadding()
     int m_padding;
 
+    virtual void AddChildGTK(wxWindowGTK* child);
+
     DECLARE_DYNAMIC_CLASS(wxNotebook)
     DECLARE_EVENT_TABLE()
 };
 
-#endif
-    // __GTKNOTEBOOKH__
+#endif // _WX_GTKNOTEBOOK_H_