Update to XML Schemas

["Drummond Reed" <drummond.reed@cordance.net>]

Dave,

A reminder that we need to update our reference in the Synax spec to XML
Schemas. The Metadata spec also needs to reference it, and it's been rev'd
to the "Second Edition". The editors are the same, so I think the reference
text just needs to be updated to:

P. Biron, A. Malhotra, XML Schema Part 2: Datatypes Second Edition W3C
Recommendation, http://www.w3.org/TR/xmlschema-2/, October 2004.

=Drummond