* 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.
+* (T49162) Installer will default to setting CACHE_ACCEL as the main cache type
+ if it is available.
=== External library changes in 1.27 ===
==== Upgraded external libraries ====