Intel GM45 GPU hangs, PC-BSD 11.0-CURRENT, sysctl hw.dri.0.info.i915_error_state

[Graham Perrin]

This is in response to December's
<https://lists.freebsd.org/pipermail/freebsd-x11/2015-December/017039.html>
(the list server seemed to omit attachments from January's
<https://lists.freebsd.org/pipermail/freebsd-x11/2016-January/017103.html>).

dmesg output from PC-BSD 11.0-CURRENTNOV2015, which does not suffer
from blackouts:
<http://pastebin.com/hrBZpCjE>

dmesg output from a verbose boot of PC-BSD 11.0-CURRENTFEB2016:
<http://pastebin.com/13y2fbG7>

December, January and February distributions of CURRENT are very prone
to blackouts with this hardware. Maybe easiest to reproduce by
launching GNOME System Monitor; for me a blackout occurs almost
immediately, or within a few seconds.