* $wgMaxUserDBWriteDuration added to limit huge user-generated transactions.
Regular web request transactions that takes longer than this are aborted.
* Added a new hook, 'TitleMoveCompleting', which runs before a page move is committed.
+* $wgCdnReboundPurgeDelay was added to provide secondary delayed purges of URLs
+ from CDN to mitigate DB replication lag and WAN cache purge lag.
=== External library changes in 1.27 ===
==== Upgraded external libraries ====