Change the rss_delete_file() functions to have a better name

Be aware that Chrome does not support RSS. Make sure RSS feeds are enabled. There is the site setting enablerssfeeds plus per module settings like data_enablerssfeeds for the data, forum and glossary activities. Also be aware that each activity instance will have RSS settings. Create a forum, a database and a glossary if you don't already have one. Check that each activity has RSS enabled. For each activity do the following: 1) add a post/entry and check that it appears in the RSS feed. 2) delete that post/entry and check that it is removed from the RSS feed. You may see "Error reading RSS data" if you just deleted the only item but the important thing is that the item is gone from the feed. Finally, go to your user's blog and check that their blog's RSS feed updates when you add an entry, when you edit an entry and when you delete an entry.