Added wxDataViewListIndexModel::Reset(), clarified and corrected wxDataViewModel::Cleared(), corrected sample

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@50768 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/dataview.h

@@ -417,6 +417,8 @@ private:
     friend class wxDataViewCtrlDCImpl;
     friend class wxDataViewColumn;
     friend class wxGtkDataViewModelNotifier;
+    friend class wxDataViewCtrlInternal;
+    
     GtkWidget               *m_treeview;
     wxDataViewModelNotifier *m_notifier;
     wxDataViewCtrlInternal  *m_internal;