WebDAV allows to some degree to contain unknown XML content inside of WebDAV
XML entities. For example, <prop> may contain not only WebDAV properties, but
also any other fancy content. This is called "extension points".
The problem is that this unknown content might already be prefixed, but webdav-
interop adds another prefix to it (because the fancy content has the same token
name, but is using a different prefix).
Solution: The prefix must only get added to elements which do not have a
prefix currently. The XSL that would do this is contained in
optimized_prefix.xsl, which was deleted hastily...