Rebase criu-dev branch on 4.0 release

[rst0git]

Hi @avagin, would it be possible to update the version of CRIU in the criu-dev branch?

Currently, this is set (in Makefile.versions) to 3.18. However, in go-criu and runc we assume that if the CRIU version includes a git ID, the minor version should be incremented by one: https://github.com/checkpoint-restore/go-criu/blob/39135d0112fa0fb12e80ba04ef843eea097add46/main.go#L253