Author: Brendan Heywood
MDL-71068 login: Fix edge cases with $CFG->protectusernames
http://git.moodle.org/gw?p=moodle.git;a=commit;h=23cc13e8ef2b9123f5320b223fcde71a9a4643b4
http://github.com/moodle/moodle/commit/23cc13e8ef2b9123f5320b223fcde71a9a4643b4
+ 3.9 en [emailpasswordconfirmmaybesent,core]