Author: Matt Davidson
MDL-55791 admin: maintenance mode access capability
Add capability to allow certain non-admin users through maintenance
mode.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=59c66f926fe794d570fe1507767aceb13d907478
http://github.com/moodle/moodle/commit/59c66f926fe794d570fe1507767aceb13d907478
+ 3.2 en [site:maintenanceaccess,core_role]