Propagate exit code in auto_extract
Hide detailed wget output; it causes trouble with non-tty output

If anyone dislikes this, I can make it detect whether stderr is a tty or not, but that'd add extra code that I can't see anyone who'd really benefit from. People on slow connections, perhaps?
Don't attempt to preserve owner when extracting as root

This causes trouble when the files are on a remote filesystem, and the user with the UID that owns the archive may not even exist.