Frees iter.
Returns a newly created child of parent, or %NULL if the iter has no child.
See poppler_layers_iter_new() for more information on this function.
Returns the title associated with iter. It must be freed with
g_free().
Sets iter to point to the next action at the current level, if valid. See
poppler_layers_iter_new() for more information.
Creates a new #PopplerLayersIter as a copy of
iter. This must be freed with poppler_layers_iter_free().