Update i915 GPU driver to Linux 3.8
Our kernel-side i915 GPU driver is getting old: platforms starting with Haswell are not supported at all.
Current status (2015-07-03)
After several months of stagnation, the work on i915 was resumed. It happens on GitHub: https://github.com/freebsd/freebsd-base-graphics/tree/drm-i915-update-38
No need to try it, the driver does not compile right now. It is still at a very early stage, but we hope to have something to test around September.