Some fixes, added Twitter plugin

Hi, glad to find someone else also keeping FeedOnFeeds working. I'd made my own modernization fork from the original before I found yours.  Looks like you're further along, so I'm switching to using yours as the upstream.

This pull request includes a few fixes for functions which have been deprecated in php 5.3 (split and ereg), and also adds a very basic share-on-Twitter plugin (which is way more useful than del.icio.us).