[CRIU] Fix building against 4.18

[Adrian Reber]

In one of the patch discussion about 4.18 it was mentioned that maybe
it would make sense to pull in the aio kernel headers into CRIU.

With the following two patches travis is really happy and CRIU
passes compile and test again also with 4.18.

There has been some movement on the kernel side, so not sure if we
should really merge this patch or not:

https://lore.kernel.org/lkml/20180708204359.GA19198@lst.de/

Maybe merge it now and revert it later once the kernel is fixed.

		Adrian