[Radiant] Sitemap doesn't validate

[Sean Cribbs]

> As for the naming of these tags, what sounds most idiomatic:
>
> <r:if_children> and <r:unless_children>
> <r:has_children> and <r:has_no_children>
> <r:is_parent> and <r:is_childless>
>
> I'm favouring the first.
>   
So am I, as it resembles the other tags in the core.  If you can get a 
patch with thorough tests to me today via Trac, I can get it into 0.6.4.

Sean