Author: rwijaya
MDL-42338 lti_mod: convert hardcoded string.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=4f718dc60c84d1242fd2953c296f24e52dbbf74e
http://github.com/moodle/moodle/commit/4f718dc60c84d1242fd2953c296f24e52dbbf74e
+ 2.4 en [submissionsfor,mod_lti]