Author: Petr Škoda
MDL-8249 improve custom role strings
Credit goes to Michael de Raadt.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=ef7090522d45b962713bc3e0e6e0009b29668289
http://github.com/moodle/moodle/commit/ef7090522d45b962713bc3e0e6e0009b29668289
+ 2.4 en [customrolename_help,core_role]
+ 2.4 en [roleshortname_help,core_role]