diff -r 07239de796bb -r e756a8c72c3d cms/drupal/modules/locale/locale.api.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/cms/drupal/modules/locale/locale.api.php	Fri Sep 08 12:04:06 2017 +0200
@@ -0,0 +1,41 @@
+<?php
+
+/**
+ * @file
+ * Hooks provided by the Locale module.
+ */
+
+/**
+ * @addtogroup hooks
+ * @{
+ */
+
+/**
+ * Allows modules to define their own text groups that can be translated.
+ *
+ * @param $op
+ *   Type of operation. Currently, only supports 'groups'.
+ */
+function hook_locale($op = 'groups') {
+  switch ($op) {
+    case 'groups':
+      return array('custom' => t('Custom'));
+  }
+}
+
+/**
+ * Allow modules to react to language settings changes.
+ *
+ * Every module needing to act when the number of enabled languages changes
+ * should implement this. This is an "internal" hook and should not be invoked
+ * elsewhere. The typical implementation would trigger some kind of rebuilding,
+ * this way system components could properly react to the change of the enabled
+ * languages number.
+ */
+function hook_multilingual_settings_changed() {
+  field_info_cache_clear();
+}
+
+/**
+ * @} End of "addtogroup hooks".
+ */