Update to 3.20130518. From the changelog:

* Fix test suite to not fail when XML::Twig is not installed. Closes:
  #707436
* theme: Now <TMPL_IF THEME_$NAME> can be used in all templates
  when a theme is enabled.
* notifyemail: Fix bug that caused duplicate emails to be sent when
  site was rebuilt.
* bzr: bzr rm no longer has a --force option, remove
Updated www/ikiwiki to 3.20130518