Stefan Monnier writes:
>> Attached. I had to go another route, though; turns out the `parse-ns'
>> argument is already overloaded in `xml-parse-tag' (it can be used to
>> provide a namespace->URI mapping), but that wasn't mentioned in the
>> other parse functions. So I had to introduce an additional argument.
>
> I'd seen that, indeed, but I think that since this parse-ns arg is
> mostly passed around and only finally used in one place, I'd rather not
> add an argument but instead pass both values via the single
> parse-ns argument.  parse-ns could then be:
> - nil as before.
> - an alist of namespace->URI.
> - a cons cell (symbol-qnames . ALIST) which does the same as the
>   previous one but uses symbols instead of cons cells for qnames.
> - the symbol `symbol-qnames' to mean (symbol-qnames . STANDARD-ALIST).
> - t to mean STANDARD-ALIST.
> The last two are only allowed when entering xml-parse-region but not in
> recursive calls (and not in calls to xml-maybe-do-ns).

That's... uh... creative. ;-) 

Anyway, it's a very seldom used feature, so I just implemented what you
suggested. Updated ChangeLog:

lisp/xml.el:

(xml-node-name): Mention `symbol-qnames' in doc-string.
(xml-parse-file, xml-parse-region): Explain PARSE-NS argument in the
doc-string.
(xml-maybe-do-ns): Return expanded name as symbol instead of cons
depending on new `simple-qnames' argument.
(xml-parse-tag-1): Deal with new PARSE-NS argument definition.  Add
`symbol-qnames' to other function calls that need it.
(xml-parse-attlist): Add `symbol-qnames' argument.

url-dav.el:

(url-dav-supported-p): Added doc-string and remove check for feature
`xml' and function `xml-expand-namespace' which never existed in Emacs
proper.
(url-dav-process-response): Remove all indentation from XML
before parsing.  Change call to `xml-parse-region' to do namespace
expansion with simple qualified names.
(url-dav-request): Add autoload.
(url-dav-directory-files): Properly deal with empty directories.  Call
hexify before generating relative URLs.
(url-dav-file-directory-p): Fix bug when checking for 'DAV:collection
(resources are returned as a list).


-David