Author: Hugh Davenport
MDL-35852 Add config option to prevent changes to configexecutable settings
http://git.moodle.org/gw?p=moodle.git;a=commit;h=9a2b5e0b4f28aac950934d6e1c9fa1aee3574f5b
http://github.com/moodle/moodle/commit/9a2b5e0b4f28aac950934d6e1c9fa1aee3574f5b
+ 2.5 en [execpathnotallowed,core_admin]