Author: David Mudrak
MDL-23709 Added more checks to prevent multiply submissions per user
http://git.moodle.org/gw?p=moodle.git;a=commit;h=2e7bd6c2864600865655ecc7446b2c1d76047937
http://github.com/moodle/moodle/commit/2e7bd6c2864600865655ecc7446b2c1d76047937
+ 2.0 en [err_multiplesubmissions,mod_workshop]