cache end line, for rapid testing whether an iterator is the end iterator

cache end line, for rapid testing whether an iterator is the end iterator

2000-08-31  Havoc Pennington  <hp@pobox.com>

* gtk/gtktextbtree.c (GtkTextBTree): cache end line,
for rapid testing whether an iterator is the end iterator
(gtk_text_btree_new): init end line cache
(gtk_text_line_is_last): use fast cached line to
see if we're the last line.
(get_last_line): use cached line here too, should
speed up some random unrelated code.