add some more stamp checks (pointed out by Anders Carlsson)

add some more stamp checks (pointed out by Anders Carlsson)

Mon Jan 21 01:21:54 2002  Kristian Rietveld  <kris@gtk.org>

        * gtk/gtktreestore.c: add some more stamp checks (pointed out
        by Anders Carlsson)

        * gtk/gtktreemodelsort.c (gtk_tree_model_sort_insert_value): don't
        assume _row_changed will insert sort (because _row_changed doesn't
        need to follow this signal), so apply insert sort here
        (gtk_tree_model_sort_level_find_insert): header doesn't need to be
        set here, so use a return instead of g_return_val_if_fail.