+* Added a hook, "ApiOpenSearchSuggest", to allow extensions to provide extracts
+ and images for ApiOpenSearch output. The semantics are identical to the
+ "OpenSearchXml" hook provided by the OpenSearchXml extension.
+* PrefixSearchBackend hook now has an $offset parameter. Combined with $limit,
+ this allows for pagination of prefix results. Extensions using this hook
+ should implement supporting behavior. Not doing so can result in undefined
+ behavior from API clients trying to continue through prefix results.
+
+==== External libraries ====
+* MediaWiki now requires certain external libraries to be installed. In the past
+ these were bundled inside the git repository of MediaWiki core, but now they
+ need to be installed separately. For users using the tarball, this will be taken
+ care of and no action will be required. Users using git will either need to use
+ composer to fetch dependencies or use the mediawiki/vendor repository which includes
+ all dependencies for MediaWiki core and ones used in Wikimedia deployment. Detailed
+ instructions can be found at <https://www.mediawiki.org/wiki/Download_from_Git#Fetch_external_libraries>.
+* The following libraries are now required:
+** psr/log 1.0.0
+*** This library provides the interfaces set by the PSR-3 standard (<http://www.php-fig.org/psr/psr-3/>)
+ which are used by MediaWiki interally by the MWLogger class.
+*** See the structured logging RfC (<https://www.mediawiki.org/wiki/Requests_for_comment/Structured_logging>)
+ for more background information.
+** cssjanus/cssjanus 1.1.1
+*** This library was formerly bundled with MediaWiki core and has now been removed. It automatically
+ flips CSS for RTL support.
+** leafo/lessphp 0.5.0
+*** This library was formerly bundled with MediaWiki core and has now been removed. It compiles LESS
+ files into CSS.
+** cdb/cdb 1.0.0
+*** This library was formerly a part of MediaWiki core, and has now been split out into a separate library.
+ It provides CDB functions which are used in the Interwiki and Localization caches. More information
+ about the library can be found at <https://www.mediawiki.org/wiki/CDB>.