(bug 42513) mediawiki.Uri: Fix parsing of URIs with @ in path.

(bug 42513) mediawiki.Uri: Fix parsing of URIs with @ in path.

The regexes for URI parsing in mediawiki.Uri did not make sure
there were no slashes (/), question marks (?) or hashes (#) in
the username or password of the URI. As a result an @ symbol
later on in the url messed up the result.

This commit fixes the regexes so that URIs with an @ symbol in
the path, query, or fragment don't get interpreted as having
a username when they actually don't.

Change-Id: I4954bfd3750d5c990e91cc0dc8a175225ccbad1e