terminal/ssh: use ioctl wrappers from x/sys/unix Use the ioctl wrapper functions from x/sys/unix instead of manually re-implementing them. Change-Id: I224de0c6ec7439dfd8c45c72071c947be8813d6a Reviewed-on: https://go-review.googlesource.com/75991 Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>