Author: Brendan Heywood
MDL-69265 email: Add admin setting for email headers
http://git.moodle.org/gw?p=moodle.git;a=commit;h=0f89884980fb9f4161765bc24664a31441bd40f5
http://github.com/moodle/moodle/commit/0f89884980fb9f4161765bc24664a31441bd40f5
+ 4.0 en [configemailheaders,core_admin]
+ 4.0 en [emailheaders,core_admin]