Git commits in Moodle 3.5.6 by Leon Stringer

commit f9ea236c4ff55b18ea80eee8c479a03fadb6cf65
Author: Leon Stringer <leon@priorsvle.com>
Date:   Fri, 29 Mar 2019 23:56:18 +0800
Tag:    v3.5.6

MDL-64719 cache: Implement purge_current_user() in \cache