This update brings Linux 4.11 KMS to recent CURRENT and 11-STABLE.
poudriere tested on 11-STABLE and recent CURRENT. Runtime tested by a range of people on Haswell, Broadwell, Skylake, Kaveri, Carrizo, Polaris on HEAD.
After discussion with @swills , use the Linux release ID as the PORTVERSION (switched between 11-STABLE and CURRENT) to avoid confusion "port is g20180224". This solution is still ugly but it allows users of the port to seamlessly upgrade, without needing to know which DRM their release supports (and get a new DRM automagically if the requirements are MFC'd).