resort if we're already in 'unsorted' state, and update the docs

resort if we're already in 'unsorted' state, and update the docs

Thu Apr 25 00:26:34 2002  Kristian Rietveld  <kris@gtk.org>

        * gtk/gtktreemodelsort.c (gtk_tree_model_sort_reset_default_sort_func):
        resort if we're already in 'unsorted' state, and update the docs