(bug 30236) Links like [[//example.com Link text]] were parsed as an internal link...

(bug 30236) Links like [[//example.com Link text]] were parsed as an internal link rather than an external link surrounded by brackets, like [[example.com Link text]]. Was caused by another pointless \b directly preceding wfUrlProtocols() in a regex. Also add a parser test for the [[http://example.com Link text]] case (the existing test only covered [[http://example.com]]) and add protocol-relative counterparts for both tests.