uncontrollable brightness with PC-BSD 11.0-CURRENT

[Graham Perrin]

HP EliteBook 850 G2; IntelCorei7-5500U with Intel HD Graphics 5500.

>From <https://forums.pcbsd.org/thread-20149-post-112331.html#pid112331>
for 11.0-CURRENTNOV2015:

> neither soft nor hard control of brightness (the soft control is
> present but ineffective)

>From <https://forums.pcbsd.org/thread-20149-post-112463.html#pid112463>
for 11.0-CURRENTDEC2015:

> as before, brightness is uncontrollable.