ssh/terminal: add support for zos

Fixes golang/go#42496

Change-Id: Iae2ddb916904d9b3947bec9638c9fbf892df7b7c
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/269177
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Trust: Tobias Klauser <tobias.klauser@gmail.com>
Trust: Michael Munday <mike.munday@ibm.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
2 files changed