In smart_rename, restore at least the regular permissions bits.

But don't try to chown or set special bits. This fixes several ports.

ok deraadt@

Using #ifndef __OpenBSD__, disable the really dangerous and silly
setuid-preserving code in the so-called smart_rename() function. I
don't want my tools (ar, ranlib, objcopy, strip) going through the
effort to preserve setuid bits on ``build-directory'' files when they
sense a symbolic link, thank you very much. The modern way is to build
code, then set such modes at install-time.

Our kernel goes through the effort to clear setuid flags, and this was
neutering that attempt. Also has atrocious error handling.

(Identified as an issue of concern while doing the audit for pledge)
ok guenther

branches: 1.1.1;
Initial revision