Author: Huong Nguyen
MDL-61921 admin: Support XOAUTH2 for outgoing mail
http://git.moodle.org/gw?p=moodle.git;a=commit;h=bc80531188d26688f23b9cb18dd3556342a08567
http://github.com/moodle/moodle/commit/bc80531188d26688f23b9cb18dd3556342a08567
+ 4.1 en [configsmtpoauthservice,core_admin]