'stty exta' (DEC support for 19.2 DZ-11)

[Joe Kelsey]

I think you can infer a definite commitment by DEC to support 19.2K
baud on DZ-11s from the fact that VMS V3.0 and beyond have all had
19.2K baud as one of the options for terminal speed.  The VMS autobaud
code will also autobaud a DZ11 at 19.2K!  If DEC ever decided to remove
support for this option, they would have to face so much internal
pressure against it, that it would never happen.

So, don't worry about using an undocumented feature of the DZ11 - DEC
uses it and even implicitly supports it via VMS, so UNIX might as well
support it also!

/Joe