Automatically bind its in Ducktype

One more Ducktype change before 1.0. I decided to automatically bind
the its namespace prefix to the ITS namespace URI. In XML, the xml
prefix is automatically bound, and we followed that in Ducktype. You
would use the xml prefix for e.g. the xml:space attribute.

I believe ITS attributes, especially its:translate, are every bit as
important and cross-format as xml:space, and if XML were designed
today, we'd give ITS the same preferential treatment as xml:space. I
also want to make it as easy as possible for people to use ITS.

http://projectmallard.org/ducktype/1.0/duck_directive#namespace

This almost certainly has no adverse effects on any existing documents,
unless you're binding the its prefix to something else. If you're
already using ITS, you can drop the @namespace directive for it, but
you don't have to.

--
Shaun