03205a8955
Audit language names against BCP 47 validator and rename those which are
not valid BCP 47 codes, leaving the old aliases for backward-compatibility.
Validated against IANA registry at
https://www.iana.org/assignments/language-subtag-registry/language-subtag-registry
with the help of the validator at
http://schneegans.de/lv/
Add fully-expanded aliases for zh-XX language codes to help compatibility
with other BCP 47 users.
See also:
1113b1203c/languages/LanguageCode.php (L56)