Git commits in Moodle 2.9.0 by Wesley Situ

commit 7be4cf1873e01f144f461a996a821cfcd259d1b8
Author: Wesley Situ <wsitu@oid.ucla.edu>
Date:   Wed, 21 Jan 2015 03:27:36 +0800
Tag:    v2.9.0-beta

MDL-48916 atto_undo: Clarify text for "Undo/Redo"