Parse date with 2-digit year fails

[tanriol]

https://www.mozdev.org/bugs/show_bug.cgi?id=24369

If the short form of the year is used in dates in an rss2 feed, what is in fact very uncommon, but allowed by the specification ( http://cyber.law.harvard.edu/rss/rss.html ), parsing the date fails. So after every update all post are marked as unread. For an example see http://www.gruene.de/uploads/tx_rsmfeedmaker/startseite.xml .