Allow `bootp` to run `suid` about bootp HOT 2 CLOSED

There will not be any special commandline options, instead I will use the standard SUID method for this. So this either works with filesystem SUID bit or transparently with suid.

I am not completely sure if bootp is allowed to drop privileges after acquiring all the ports or only must drop privilege before calling the scripts, though.

Implementing that is relatively easy:

If effective UID (which always is 0) is not the same as the real UID,
then drop privileges to the real UID. (Do the same for GID, first.)

Only the location where to do this is unknown.

from bootp.

Implemented in db29365

AFAICS this works at my local site.

from bootp.