Git commits in Moodle 2.5.1 by Andrew Davis

commit a1d43d9e4f52ebf1c2bd6a2d3f5e0bf7268a410d
Author: Andrew Davis <andrew@moodle.com>
Date:   Mon, 28 Jan 2013 12:03:59 +0800
Tag:    v2.5.1

MDL-36090 core_grade: added logging of overriding of student grades