User:Liangent/wb-lang/updates

Merged

 * Lib: Language work infrastructure is done (class LanguageWithConversion, LanguageFallbackChain and LanguageFallbackChainFactory). 70871 71778 performance tweaks
 * Repo: A new special page, Special:MyLanguageFallbackChain, is added, to display the language fallback chain used for current context, allowing users to confirm their user settings now. 71281
 * Repo: Various page titles, including view, edit and history, as well as displayed text of links to item pages (on special pages), are better displayed. 71845 71865
 * Client: is now able to display labels from variant languages, as properly converted text. 71072 71996

Pending

 * Lib: Serialized formats get a new field "source-language", alongside with "language", to indicate the language where this particular piece of data was fetched. 72225
 * Client: Lua: mw.wikibase.labels now finds labels in all variants. 72751
 * Lib: A new pseudo language code, "qqc", is introduced to contain the most preferred label for current context. 72258
 * Repo: wbEntity and wbUsedEntities now get contents in "qqc" 72226
 * Repo: api.php?action=wbgetentities now accepts a new parameter, &contextlanguage=. 72260