Bug#884116: linux-image-4.9.0-3-amd64: screen artifacts then crash without anyway to revert to console

[Mathias Bavay]

I am replying to myself: in fact, after a few days of using kernel 4.14.0
backport, I had a series of crashes Today. So it makes things much better,
but not crash-free yet (still using the same theme with lots of
transparency effects).

Mathias