Correctly handle <abbr> followed by ISBN

Correctly handle <abbr> followed by ISBN

Bug 22905.  Patch based on one submitted by Solitarius.  Basically, we
were assuming that anything matching <a.*?</a> was a link and ignoring
it so as to avoid nested links, but that matched the HTML from

<abbr>(fr)</abbr> ISBN 2753300917 [http://www.example.com example.com]

so the ISBN didn't work.  Parser test committed, fails without the
Parser.php change.