Load a Hebrew string such as "ה" into a Pango layout and try to iterate by
char. It will crash on the first call to pango_layout_iter_next_char, failing an
assertion after calculating new_index which becomes negative.

// Code illustrates approach but is not actual problem 
// code and has not been run:
char *s="ה";   // \xd7\x94
pango_layout_set_text(layout, s, strlen(s));
PangoLayoutIter *iter = pango_layout_get_iter (layout);
while (pango_layout_iter_next_char (iter)) {

   This failed both with the version of Pango/GTK+ from Fedora Core 2 and with a
copy of pango_layout_iter_next_char extracted from the most recent Pango source
distribution.