Hi,

I have implemented a new option keyword, RSS_FEED_URL, for the RSS
exporter backend.

The RSS_FEED_URL goes into the atom:link element that identifies the
feed's own URL.

http://www.rssboard.org/rss-profile#namespace-elements-atom-link

Currently, the feed URL is assumed to be html-link-home or
publishing-directory concatenated with the output filename of the
feed. This need not necessarily be so. So, the RSS_FEED_URL option
keyword is introduced to let the user customize the feed URL.

Please review the patch and consider for inclusion.

Thanks,
Arun Isaac.