So short of re-implementing an entire new PSHost for non-interactive
sessions, this is a work-around. If a script (file or command) is passed
to the shell, we tunnel that information through to the raw UI so it can
skip calling out to the TTY (which may not exist).
There has to be a better way to do this, but the structure of PSHost >
UI > Raw UI just makes this incredibly difficult.
The former is available, the latter is not. For our simple case of a
readline-esque shell on Linux, they seem equivalent. This removes the
import of libpsnative and the native calls to get terminal width/height.
Andrew Schwartzmeyer