Allow localization of language names in multisite

[pavelevap]

There is Site Language settings in multisite (General Options). But all available languages are in English, so there is English, Czech, etc. But when I switch to Czech language, there is still only Czech and not "Čeština". I am not sure if there is need to translate all languages, but there should be localized at least selected language (or all available languages).

It is caused by function format_code_lang() in ms.php (line 463) where are all language names hardcoded in English.

This may warrant a separate ticket, but it seems that the list is hardcoded, with a set of locales which is partly out of date (example: no value for Brazilian Portuguese, pt_BR)

more info:
​http://wppolyglots.wordpress.com/2012/06/06/is-it-possible-to-translate-the-word/

and:
http://core.trac.wordpress.org/browser/trunk/wp-admin/includes/ms.php#L423

Related: #13069