Uses XML output format of svn info to fetch url

Regex was used with svn info output to fetch url value in
SVN._sourcedirIsUpdatable. French and Norvegian svn versions use
respective language names for url value and not 'URL' in regex.
XML Output format of svn info resolves it

Fixes http://trac.buildbot.net/ticket/2375
Fixes svn tests to match url value in XML output format of svn info