`su'.
* The `usermod' from `shadow' allows setting a supplementary group
equal to the user's primary group, so the special hack for the
`nixbld' group is no longer needed.
* Removed /etc/default/passwd since it's not used by the new passwd.
The hash is configured in pam_unix.
* Move some values for `security.setuidPrograms' and
`security.pam.services' to the appropriate modules.
svn path=/nixos/trunk/; revision=22107