Motivation:

class Language contains a lot of public and unused members. A few of them:

• public $mVariants - isn't even assigned
• public $mLoaded - isn't even assigned
• public $mMagicExtensions = []; - assigned and even has redundant logic:

https://codesearch.wmflabs.org/search/?q=mMagicExtensions&i=nope&files=&repos=

• private $mParentLanguage = false; - isn't used
• public $transformData = [];

...
etc.

This introduces difficulties in supporting further versions.

Expected result:

• Unused variables should be removed.
• Variables that isn't used from outside should be protected/private
• changed variables should be deprecated.