In Drupal 7 hook_multilingual_settings_changed() was introduced to respond to changes in the list of languages or to the removal of a language. This was not always invoked though and did not provide any information as to what changed more specifically, so Drupal 8 standardizes on node API-like hook names for languages.
See http://api.drupal.org/api/drupal/modules--locale--locale.api.php/functio...
New hooks:
- http://api.drupal.org/api/drupal/modules--locale--locale.api.php/functio...
- http://api.drupal.org/api/drupal/modules--locale--locale.api.php/functio...
- http://api.drupal.org/api/drupal/modules--locale--locale.api.php/functio...