* Fix for r41340, r96405, r97849: introduce a function which gets the current content...

* Fix for r41340, r96405, r97849: introduce a function which gets the current content language, called Parser::getTargetLanguage() following the ParserOptions terminology, and added doc comments, to improve the chances of a human being able to work out what is going on. Just because a function happens to do the thing you want doesn't mean you should call it.
* The language object used for lc() in Parser::braceSubstitution() must match the one used in setFunctionHook() during firstCallInit(). It can't change depending on what message you are parsing. Use $wgContLang like before r97849.