xml2 contrib patch supporting default XML namespaces

Attatched you'll find a patch that I've been kicking around for a
while that I'd like to propose for inclusion in 8.3. I attempted to
submit this through the original xml2 author (as far back as the 7.4
days) but got no response.

It's really fairly trivial, but I will be using the features it
provides in production soon, so I'd like to see it applied against the
contrib xml2 module. The patch adds support for default XML
namespaces in xml2 by providing a mechanism for supplying a prefix to
a named namespace URI. It then wraps the namespace-capable functions
in backward-compatible equivalents so that old code will not break.

I have patched README.xml2, pgxml.sql.in and xpath.c against CVS HEAD
as of about 1 hour ago. I have code that uses both the old
non-namespace-capable functions and the new functions, and all
function as intended in my environment.

Please let me know if there is any more I can/need-to do to help this
patch along!

--
Mike Rylander
mrylander(at)gmail(dot)com
GPLS -- PINES Development
Database Developer
http://open-ils.org