MI testsuite improvements

[Bob Rossi]

> Please, one change, one patch.

Sorry, still a little new to this.

> >   - Gives the inferior it's own PTY to send output to
> 
> I'm ok with this, as I think you noted elsewhere, this has become the 
> defacto standard.  Would you be interested in documenting this?

Sure, where thought?

> The change should be applied to just mi-* and not mi2-*, and should only 
> accept plain text on that PTY.   @... output on the PTY should be 
> rejected ("in theory" so should anything on GDB's pty).

Just curious, why are you interested in only applying changes to mi-* and 
not to mi2-*?

Thanks,
Bob Rossi