$user: User whose preferences are being used to make timestamp
$lang: Language that will be used to render the timestamp
+'GetSlotDiffRenderer': Replace or wrap the standard SlotDiffRenderer for some
+content type.
+$contentHandler: ContentHandler for which the slot diff renderer is fetched.
+&$slotDiffRenderer: SlotDiffRenderer to change or replace.
+$context: IContextSource
+
'getUserPermissionsErrors': Add a permissions error when permissions errors are
checked for. Use instead of userCan for most cases. Return false if the user
can't do it, and populate $result with the reason in the form of