Zabbix

........S. [ZBXNEXT-6820] added utf8mb3 when checking for supported mysql character sets and collations

Merge in ZBX/zabbix from feature/ZBXNEXT-6820-5.0 to release/5.0

* commit '3a62b60e685a3ae1bb6f3ea640573c192aa6c5d7':
  ........S. [ZBXNEXT-6820] fixed warning
  ..F....... [ZBXNEXT-6820] added utf8mb3_bin to mysql allowed collation
  ..F....... [ZBXNEXT-6820] added utf8mb3 encoding to allowed for mysql
  .D........ [ZBXNEXT-6820] added changelog entry
  ........S. [ZBXNEXT-6820] added utf8mb3 support for mysql