Author: Paul Holden
MDL-69788 admin: validate language menu configuration.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=c651779095c853d54da93c3087c780e8d286072d
http://github.com/moodle/moodle/commit/c651779095c853d54da93c3087c780e8d286072d
+ 3.9 en [invalidlanguagecode,core_error]