Consider a different list-order for locales in language menu

@pierov I noticed that options listed in the about:preferences#general Language menu in the multi-locale testbuild are in latin-alphabetical order. This has the strange affect of pushing locales that use special latin characters after the standard A→Z, and all non-latin locales to the very bottom of the list:

www.torproject.org lists locales by IETF language code instead, which seems useful. What would your advice here be @emmapeel?