Git commits in Moodle 3.6.6 by Neill Magill

commit 0d51c25e85d30e2ce40929633af9c6c56233fb96
Author: Neill Magill <neill.magill@nottingham.ac.uk>
Date:   Wed, 21 Aug 2019 16:02:03 +0800
Tag:    v3.6.6

MDL-65443 core: Improve class descriptions for locking events

commit e8b4c32290e26fd4a8e36dc29496fe597f02a155
Author: Neill Magill <neill.magill@nottingham.ac.uk>
Date:   Fri, 09 Aug 2019 18:27:40 +0800
Tag:    v3.6.6

MDL-65443 core: Log when a context is locked or unlocked