wp_list_cats is not closing the </li> and so doesn't validate as XHTML

[MikeLittle]

As reported by Ajay D'Souza on the testers mailing list. The newly restructured wp_list_cats() which calls (eventually) wp_list_categories() does not correctly close the list item (li) elements.
The fix is to add a fourth argument $args to the function end_el() in the class Walker_Category.
The function references $args to determine whether to add the closing tag.

Patch to follow.

[MikeLittle]

Fix for ticket 2668

[ryan]

(In [3715]) Don't forget to pass args. Props Mike Little. fixes #2668