[enhancement] Add RSS/Atom feed for failed builds (skipped ones too?).

[OscarL]

After a few days of new/updated recipes on HaikuPorts, it is a bit too tedious to try to find a failed build (and its log) while using the "previous/next" buttons on the buildmasters webpages.

I think that having an .rss (or atom) feed for just the failed/skipped builds would be a big improvement, and perhaps less costly (in both development and server resourcese) than other alternatives (such a "search in logs" feature).