Author: Huong Nguyen
MDL-82379 core_user: Move email change token to user private access key
http://git.moodle.org/gw?p=moodle.git;a=commit;h=bd115c5e1acdf272fdd7ec4da313a56c6bdefcb9
http://github.com/moodle/moodle/commit/bd115c5e1acdf272fdd7ec4da313a56c6bdefcb9
+ 4.1 en [auth_changingemailaddress,core_auth]