MathJax: Support localizations of MathJax

Adding the localizations which I missed when updating to 2.2 in
I9446121985ae27e65a429b5a558940ac30520d44
Forward the userlanguage from MediaWiki to MathJax
Note that MathJax preserves selected language in cookies, so once set,
you need to manually switch it every single time.

Bug: 35038
Change-Id: Ibf43a3e44ea2bfdbd9fddc01c71c72ba097ff1b7