+ * Update the redirect entry for a given page.
+ *
+ * This methods bypasses the "redirect" table to get the redirect target,
+ * and parses the page's content to fetch it. This allows to be sure that
+ * the redirect target is up to date and valid.
+ * This is particularly useful when modifying namespaces to be sure the
+ * entry in the "redirect" table points to the correct page and not to an
+ * invalid one.
+ *
+ * @param $id int The page ID to check