OK deraadt, phessler

This recycles the _btd uid/gid that have been removed in 2013.
Discussed in the hackroom.

and verify patches.
discussed with deraadt@ rpe@
ok deraadt@

defaults for building the system from source.
ok deraadt

OK deraadt@

Input deraadt@
OK benno@, sthen@

OK natano on a previous diff which used a different uid/gid.
naddy@ pointed out that uid/gid was already taken on "important" systems.
Turns out we cannot easily recycle freed up uids/gids so settle on 51.

which was a "better than nothing" measure for 5.9.
Another user to come. Approved by deraadt@ on principle.
thanks sthen@ for checking my lines over.

ok deraadt

They should not share a uid.  Leave the proxy uid for later mop-up
(sysmerge does not handle uid renamings well enough)
ok dlg, ok aja a while back

ok deraadt

multi-user builds. Discussed with espie, ajacoutot, ok deraadt

to initialize the unprivileged user, so the usual rc.d mechanism to set the
class isn't used. Problem reported by otto, ok otto@ ajacoutout@

a proper & complete bind port will show up.
discussed with many for years

used by npppd.
ok deraadt

* _afs: arla/nnpfs got disabled then removed long ago
* _kdc, _kadmin: these were added 10 years ago but never used for
anything afaict
ok dcoppa@ beck@

ok sthen@ deraadt@

the net/uccp package and is installed under /usr/local/. Since we don't
want a shell that default to /usr/local/..., use /sbin/nologin.
The uucp package will automatically change to the correct shell on
pkg_add / pkg_delete.
idea from and ok miod@

OK claudio@

with NFS here. Result of a discussion with several.
ok deraadt@ millert@

OK sobrado@, todd@

ok deraadt@

ok deraadt@

run by root, it binds a shared address to the socket, cranks the
process priority and drops privileges. sio_open(3) will try to
connect to the private socket first (if any), then to the shared
socket. Only one user may have connections to aucat at a given
time.
based on discussions with henning, pyr and others
ok jacek, deraadt

error out.
Add a new user _rwalld for rpc.rwalld, and use that instead
of nobody, also unconditionally drop to _rwalld not only
if rpc.rwalld was started with euid 0 (as root).
ok deraadt@

discussed with pyr@ and deraadt@

discussed with and ok uwe@

ok deraadt@, reyk@, pyr@

approved by deraadt@, ok thib@