Do not get "last change" marks around output

Usually when making changes in a buffer the marks `'[` and `']` get set at the start and end of where the change took place.

This does not seem to be happening in `vsh` buffers due to the output coming from the pseudo terminal.

I honestly don't know if this is something I think would be better changed.
Mostly raising the issue so that it is recorded and may be looked at in the future.