Author: Sam Hemelryk
MDL-23532 enrol - removed general handling of user enrolment editing/unenrolment plugins are now responsible for this
http://git.moodle.org/gw?p=moodle.git;a=commit;h=12a52d7c6e5ab3e19bf6fa4d65594d53b4aaa8ce
http://github.com/moodle/moodle/commit/12a52d7c6e5ab3e19bf6fa4d65594d53b4aaa8ce