MFH: r459293

databases/mysql56-{client, server}: Update to 5.6.39
This update fixes bugs like CVE-2018-2696, CVE-2018-2562,
and CVE-2018-2583 in MySQL protocol by upstream

PR: 225240
Sponsored by: Netzkommune GmbH

Approved by: ports-secteam (feld)