Git commits in Moodle 2.7.5 by Wesley Situ

commit a6a73abf88c0fbbb444aef738b93e0f0cccd305b
Author: Wesley Situ <wsitu@oid.ucla.edu>
Date:   Wed, 21 Jan 2015 03:27:36 +0800
Tag:    v2.7.5

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