[Piglit] add kernel message logging?

[Michal Suchanek]

Hello

I was thinking that it would be nice if the results also logged kernel
messages genereated by the tests.

Since the piglit tests often crash or lock up the GPU and this is
reported by the kernel it would add more useful information into the
logs.

It should be quite easy to compare the dmesg output before and after the test.

I don't know python so it would be quite difficult for me to add to
the test runner, unfortunately.

Thanks

Michal