Add wxDataViewCtrl::GTKPathToItem() function and use it.

No real changes, just refactor the code to use a function mapping GtkTreeIter
to our wxDataViewItem and use it instead of duplicating its code everywhere.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@65211 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/dataview.h

@@ -14,6 +14,8 @@
 
 class WXDLLIMPEXP_FWD_ADV wxDataViewCtrlInternal;
 
+struct _GtkTreePath;
+
 // ---------------------------------------------------------
 // wxDataViewColumn
 // ---------------------------------------------------------
@@ -171,6 +173,10 @@ public:
     GtkWidget *GtkGetTreeView() { return m_treeview; }
     wxDataViewCtrlInternal* GtkGetInternal() { return m_internal; }
 
+    // Convert GTK path to our item. Returned item may be invalid if get_iter()
+    // failed.
+    wxDataViewItem GTKPathToItem(struct _GtkTreePath *path) const;
+
     virtual void OnInternalIdle();
 
 protected: