Minor improvements

The Inform extensions page has now been upgraded so that

• The defunct “(compatible with 4S08)” tags have been removed, since they’re no longer relevant; all extensions on the page have been re-
  tested as of this afternoon and those that do not compile (and there are only a couple) have been marked accordingly.
• Extensions are now time-stamped with the date of last modification. (At the moment everything is registered to today, but new extensions will be correctly stamped as they are added.)
• New or recently updated extensions are now marked “new” or “updated.”
• Some new categories have been added to make things easier to find.
• A table of contents appears at the head of the page to make navigation easier; this also shows in which categories new or updated extensions have been filed.
• The site now has an RSS feed which will automatically carry information on any new and updated extensions as they are added.