It is still set to true for extension compatibility but doing so in extensions is deprecated.
* $wgXhtmlDefaultNamespace is no longer used by core. Setting it will no longer change the
xmlns used by MediaWiki. Reliance on this variable by extensions is deprecated.
+* $wgHandheldStyle was removed.
+* $wgJsMimeType is no longer used by core. Most usage has been removed since
+ HTML output is now exclusively HTML5.
=== New features in 1.22 ===
* (bug 44525) mediawiki.jqueryMsg can now parse (whitelisted) HTML elements and attributes.
which can be cascading (previously 'sysop' was hard-coded as the only one).
* XHTML5 support has been improved. If you set $wgMimeType = 'application/xhtml+xml'
MediaWiki will try outputting markup acording to XHTML5 rules.
+* New hook 'TitleSquidURLs' for manipulating the list of URLs to be purged from
+ HTTP caches when a page is changed.
=== Bug fixes in 1.22 ===
* Disable Special:PasswordReset when $wgEnableEmail is false. Previously one
stored in the database.
* (bug 47219) Allow specifying change type of Wikipedia feed items
* prop=imageinfo now allows setting iiurlheight without setting iiurlwidth
-* prop=info now adds the content model of the title.
+* prop=info now adds the content model and page language of the title.
* New upload log entries will now contain information on the relavent
image (sha1 and timestamp).