Author: Paul Holden
MDL-78435 mod_assign: ensure due date is always after start date.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=0f052d1c35d74288d9a7488558207df8d0d84212
http://github.com/moodle/moodle/commit/0f052d1c35d74288d9a7488558207df8d0d84212
+ 4.1 en [duedateaftersubmissionvalidation,mod_assign]