Checkpoint-restore tool v1.8

Hi, guys!

This year's winter criu is tagged, including new features (as usual) improvements for live migration, a LOT of bug fixes, closed CVEs and new zdtm test suite :)

The changelog is http://criu.org/Download/criu/1.8
Tarball with sources is https://download.openvz.org/criu/criu-1.8.tar.bz2
Repo tag is https://github.com/xemul/criu/releases/tag/v1.8

-- Pavel