unix: add PtracePeekUser

Fixes golang/go#14459

Change-Id: I9809340141dd5704d5a32a079486a1f889725541
Reviewed-on: https://go-review.googlesource.com/38638
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
1 file changed