Author: Paul Holden
MDL-77264 grade: define fallback name of abstract export event.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=4acab9aaaf3419ce23149011d8dc2e6dc9ec5d78
http://github.com/moodle/moodle/commit/4acab9aaaf3419ce23149011d8dc2e6dc9ec5d78
+ 4.0 en [eventgradeexported,core_grades]