Important: #81196 - LanguageService moved to core extension 

See forge#81196

Description 

The PHP class TYPO3\CMS\Lang\LanguageService - very well known for being available as $GLOBALS['LANG'] in the TYPO3 backend scope, and responsible for translating labels from XLF/XML files, has been moved to EXT:core, the core system extension.

The new class is named \TYPO3\CMS\Core\Localization\LanguageService . A class alias for backwards- compatibility is available, so the instantiating or referencing the old class name still works.

The class alias functionality will be dropped in TYPO3 v10.