Reserve PRI method in HTTP/1.1 to avoid collision

In http://www.w3.org/mid/5215922F.4090509@treenet.co.nz;list=ietf-http-wg, it was proposed that the PRI method be reserved in the HTTP/1.1 method registration document to avoid possible future reservation and ensure that the magic string remains a reliable way of differentiating HTTP/1.1 connections from HTTP/2.0 connections.  There was a +1 and some offline discussion along the same vein, no dissent that I heard or saw.  However, I don’t see it in http://tools.ietf.org/html/draft-ietf-httpbis-method-registrations-14, presumably because no RFC exists to reference.  The appropriate doc is probably HTTP/2.0 rather than breaking the glass on the prepopulated registrations.
Adding PRI method registration.