Deprecate $wgDeferredUpdateList

Callers should instead use DeferredUpdates::addUpdate. The
function is superior because it is able to enforce type-hinting
rather than throwing a fatal error. Also it's not a global :)

The only extension still using the global is FlaggedRevs,
for which I've submitted I1a7c6540b2.

Change-Id: Ic59c90c0d0131039295bd785280dc70ebde6e40f

RELEASE-NOTES-1.24

@@ -63,6 +63,8 @@ production.
 * The default thumb size ($wgDefaultUserOptions['thumbsize']) is now 300px, up from
   180px. If you have altered the number of entries in $wgThumbLimits for your wiki, you
   may need to adjust your default user settings to compensate for the index change.
+* $wgDeferredUpdateList is now deprecated, you should use DeferredUpdates::addUpdate()
+  instead.
 
 === New features in 1.24 ===
 * Added a new hook, "WhatLinksHereProps", to allow extensions to annotate

includes/Setup.php

@@ -595,6 +595,10 @@ if ( !is_object( $wgAuth ) ) {
  */
 $wgTitle = null;
 
+/**
+ * @deprecated 1.24 Use DeferredUpdates::addUpdate instead
+ * @var array
+ */
 $wgDeferredUpdateList = array();
 
 // Disable all other email settings automatically if $wgEnableEmail