* ParserOptions::getUserLang() will still return a string for compatibility, added ParserOptions::getUserLangObj() to get the object
* Added ParserOptions::newFromUserAndLang() and ParserOptions::newFromContext() to easily get a ParserOptions object when a context is available or when someone wants to force the language
* Updated OutputPage and Preferences to use newFromContext() and WikiPage to use newFromUserAndLang()
* ParserOptions::setUserLang() still accepts either a string or a Language object, but changed the calls to pass an object instead of a string
* Changed Parser::getFunctionLang() to return the Language object from ParserOptions when parsing interface messages rather than $wgLang directly and updated the documentation to say that $wgLang should not be used directly (as $wgUser, $wgTitle and $wgRequest)
* Do additional validation and is_array() check in LanguageConverter
* Make redirects be in content language again (remove from Title->getPageLanguage())
* Pass title object from ParserCache to ParserOptions->optionsHash
* Made variant tabs hidden on special pages (has no or sometimes wrong/inconsistent effect there; plus it's mainly in the user language)
* Made redirects be in content language again (remove from Title->getPageLanguage())
* Correct directionality when viewing diffs
* Correct arrows for Pager
* CSS/JS pages always 'en' (LTR)
* Messages on Special:Allmessages have lang and dir attributes based on the selected language
* Use ParserOptions()->getTargetLanguage() for setting the page language/direction
* Set headings on categories in user language/direction
* Only set language/direction when viewing a page (or editing but only preview and textarea)
For environments post r70783, they will need to rerender pages with __NOEDITSECTION__ or no headings (hopefully those will be simple pages).
There will be no extra parser cache misses for environments pre r70783.
Doing this allows skins to override doEditSectionLinks without poluting the parser cache or fragmenting the parser cache more.
As a side effect it eliminates the primary cause of user language based parser cache fragmentation.
Because this makes most old parser cache entries invalid $wgUseEditSectionTokens is provided so that large installations like Wikipedia can keep their old parser cache entries.
* Removed other usages of $wgUser in Parser stuff, as stated in doc
* Added mechanism to get an User object in Parser, based either on the object given in Paser::preSaveTransform() or the ParserOptions otherwise
use the same parsercache entry for articles without <math> tags.
The cache key format is kept as a fallback so the old cached entries can be reused.
Should boost parsercache hits, but it also makes easier to pollute the parsercache by tag hooks that behave
badly, directly using $wgUser or $wgLang.
Extensions hooking PageRenderingHash now see !edit=0 and the !printable=1 bits.
Fixes bug 24714 - Usage of {{#dateformat: }} in wikis without $wgUseDynamicDates can lead to unexpected results
Builds upon r70498, r70498, r70501, r70517, r70651, r70653, r70765, r70780.
