Restore overlayroot package with current version in Ubuntu.

9 years ago overlayfs module was not in Debian and (according to the bug report) Overlayroot is not able to create the fstab for aufs.

So 8 years ago it made sense to remove the overlayroot package.

Now overlayfs is stable and in mainline Linux, so overlayroot can be put back.

Restoring the package from 8 years ago did not build, so I pulled in the upstream changes as that is what I have been working with on a personal project, so I have confidence in it.