Attached is a patch that should add proper BSD_SOURCE support for
<unistd.h>. I'm not sure that the formatting/style is proper, and the
exact arrangement is rather arbitrary.  But I've moved a lot of things
that were wrongly grouped in either ANSI namespace or GNU-only
namespace.

BSD || XOPEN means the macro test should be
#if defined(_BSD_SOURCE) || defined(_XOPEN_SOURCE)
I see glibc turns on both of these with _GNU_SOURCE.

Misplaced (should be BSD || XOPEN):
(Properly, these require XOPEN >= 500)
usleep, ualarm, fchown, fchdir, lchown,vhangup,
apparently fsync?

Missing (BSD || XOPEN):
getwd,ttyslot,sethostid,get/setdomainname,revoke,profil,acct,get/end/setusershell

BSD||GNU:
setlogin, getpass

These and chroot also should be available with lower values of
_XOPEN_SOURCE

Incompatible:
BSD uses setpgrp the same way everyone else uses setpgid--a
substitution macro will do the job. That's what glibc does and what I
did.

And there may be one or two more that I didn't mention in here because
I lost track.

Isaac Dunham