-This has a side benefit that we take advantage of. We have
-tables "links" and "brokenlinks" which we use to do things
-like the Orphans page and Whatlinkshere page. It just so
-happens that after we update a page, we display it--and as
-we're displaying it, we look up all the links on that page,
-causing them to be put into the cache. That information is
-exactly what we need to update those two tables. So, we do
-something tricky when we update pages: just after the update
-and before we display, we clear the cache. Then we display
-the updated page. Finally, we put a LinksUpdate object onto
-the deferred updates list, which fetches its information from
-the cache.