Author: Cameron Ball
MDL-41945 mod_assign: Check if submission has been modified
This patch adds a check that stops a user submitting an assignment
if someone else has modified it in the meantime.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=3141d42c6363a70d7af5ed2b7060d9ce96218394
http://github.com/moodle/moodle/commit/3141d42c6363a70d7af5ed2b7060d9ce96218394
+ 3.1 en [submissionmodified,mod_assign]
+ 3.1 en [submissionmodifiedgroup,mod_assign]