www/gitlab: 8.5.11 -> 8.5.12 to really fix CVE-2016-4340

Changes:

https://about.gitlab.com/2016/05/02/cve-2016-4340-patches/

PR: 209225
Submitted by: Torsten Zuehlsdorff <ports@toco-domains.de> (maintainer)
Approved by: ports-secteam (junovitch)