revert inout annotation for gtk_tree_model_iter_next parameter
revert inout annotation for gtk_tree_model_iter_next parameter

* 'inout' is poorly defined and causes bugs so revert back to the default
  'in' annotation

Unity-Technologies/gtk,Distrotech/gtk,Unity-Technologies/gtk,Distrotech/gtk,johne53/MB3Gtk-2,Unity-Technologies/gtk,johne53/MB3Gtk-2,Unity-Technologies/gtk,johne53/MB3Gtk-2,Distrotech/gtk,Unity-Technologies/gtk,johne53/MB3Gtk-2,johne53/MB3Gtk-2,Distrotech/gtk,Distrotech/gtk