MPROTECT off for opera

Signed-off-by: David Sterba <dave@jikos.cz>
Set only xattr flags, add compat option for PT_PAX

By default, set only the xattrs, PT_PAX is disable in kernel. For
compatibility, there's --no-xattr option to use paxctl utility.

Signed-off-by: David Sterba <dave@jikos.cz>