New version of xmllib from Sjoerd.

New version of xmllib from Sjoerd.
The main incompatibility is that the error reporting method is now
called as
 parser.syntax_error(msg)
instead of
 parser.syntax_error(lineno, msg)

This new version also has some code to deal with the <?xml?> and
<!DOCTYPE> tags at the start of an XML document.
The documentation has been updated, and a small test module has been
created.