Git commits in Moodle 2.9.4 by Matt Petro

commit 9873593120ebffa35636aa48d80e55d75b9115d3
Author: Matt Petro <petro@engr.wisc.edu>
Date:   Tue, 22 Sep 2015 01:44:18 +0800
Tag:    v2.9.4

MDL-51482 caching: Fix unnecessary updates to lastinvalidation time