IETF examples of using "URL" rather than "URI"

[masinter]

I think for 'naming' point out that IETF authors often use
URL and not URI or IRI, e.g.,
http://datatracker.ietf.org/doc/draft-singer-appsawg-mcast-url/
just to pick a random one. Come up with more stats
on use of URL vs URI in recent IETF internet drafts and RFCs.