MediaWiki 1.21/wmf11

The latest version (labeled "1.21wmf11") of MediaWiki, the software that powers Wikipedia and its sister sites, is being deployed to all Wikimedia sites in stages, starting on Monday, 4 March 2013 (see the roadmap).

We will continue to deploy the latest software every two weeks. This is intended to minimize disruption and possible issues, and make it easier to identify the cause of problems, since the possibly problematic code will be much more recent.

Most important changes

 * - Add number of watchers to API prop=info
 * - API parameters may now be marked as type "upload", which is now used for action=upload's 'file' and 'chunk' parameters. This type will raise an error during parameter validation if the parameter is given but not recognized as an uploaded file.
 * More changing of "e-mail" to "email" in user facing text
 * - Add PagesWithProp special page and API module
 * Added an API query module list=pageswithprop, which lists pages using a particular page property.
 * Added an API query module list=pagepropnames, which lists all page prop names currently in use on the wiki.
 * - create language-specific collations for category sorting
 * - Give a 200 response for valid user pages (whether or not the user has edited the page yet)

Breaking changes

 * - Remove DB2 support (it has been unmaintained for a while)
 * - Removed the jquery.collapsibleTabs module and moved it to the Vector extension. It was entirely Vector-extension-specific, deeply interconnected with the extension, and this functionality really belongs to the extension instead of the skin anyway. In the unlikely case you were using it, you have to either copy it to your extension, or install the Vector extension (and possibly disable its features using config settings if you don't want them).