Kill EXTRACT_PRESERVE_OWNERSHIP, update some comments
There was no mention of root-squash in the commit log or in the comment so I didn't think about it.
I can put back the .if !defined(EXTRACT_PRESERVE_OWNERSHIP) around the CHMOD/CHOWN.
For --no-same-owner --no-same-permissions, I think it doesn't harm with root-squash. Do you confirm?