[gtkada] Severe bug with Gtk_Tree_Iter

[Arnaud Charlet]

> > My proposal is to initialize all intermediate Gtk_Tree_Iter objects
> > with
> > Null_Iter throughout GtkAda. It is a lot of places, but I guess it should
> > be possible to adjust the API generation script to make this
> > automatically.
> 
> It makes sense to me.

Or laternatively we could add default init value on the declaration of
Gtk_Tree_Iter itself which would take care of user declarations as well:

type Gtk_Tree_Iter is record
   Stamp : Gint := 0;
   User_Data : System.Address := System.Null_Address;
   User_Data2 : System.Address := System.Null_Address;
   User_Data3 : System.Address := System.Null_Address;
end record;

Arno