(xml-maybe-do-ns): New function to handle namespace

(xml-maybe-do-ns): New function to handle namespace
parsing of both attribute and element names.
(xml-ns-parse-ns-attrs, xml-ns-expand-el, xml-ns-expand-attr)
(xml-intern-attrlist): Remove in favor of xml-maybe-do-ns.
(xml-parse-tag): Update assumed namespaces.  Clean up namespace parsing.
(xml-parse-attlist): Make it do its own namespace parsing.