These are unused since the darwin port switched to libc calls in
CL 148457.

Change-Id: I309bb5b0a52c9069484e7a649d4a652efcb8e160
Reviewed-on: https://go-review.googlesource.com/c/go/+/200866
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>