* Added new backend to represent and store information about sites and site
specific configuration.
* jQuery UI upgraded from 1.8.23 to 1.8.24.
+* Added separate fa_sha1 field to filearchive table. This allows sha1
+ searches with the api in miser mode for deleted files.
+* Add initial and programmatic sorting for tablesorter.
+* Add the event "sortEnd.tablesorter", triggered after sorting has completed.
+* The Job system was refactored to allow for different backing stores for queues
+ as well as cross-wiki access to queues, among other things. The schema for the
+ DB queue was changed to support better concurrency and reduce deadlock errors.
+* Added ApiQueryORM class to facilitate creation of query API modules based on
+ tables that have a corresponding ORMTable class.
+* (bug 40876) Icon for PSD (Adobe Photoshop) file types.
=== Bug fixes in 1.21 ===
* (bug 40353) SpecialDoubleRedirect should support interwiki redirects.
recentchanges table.
* (bug 32951) Do not register internal externals with absolute protocol,
when server has relative protocol.
+* (bug 39005) When purging proxies listed in $wgSquidServers using HTTP PURGE
+ method requests, we now send a Host header by default, for Varnish
+ compatibility. This also works with Squid in reverse-proxy mode. If you wish
+ to support Squid configured in forward-proxy mode, set
+ $wgSquidPurgeUseHostHeader to false.
=== API changes in 1.21 ===
* prop=revisions can now report the contentmodel and contentformat, see docs/contenthandler.txt