postscript system

[MMcM@TITANIA.Oberon.Dialnet.Symbolics.COM (Mike McMahon)]

It's a moderately complete, mediocre performance, PostScript
interpreter.

Its main features:

- Display Postscript File CP command for previewing files.

- Postscript type to Concordia's m-X Create Picture command.

- Postscript file type to the Image Substrate.

- Postscript mode in the editor.
-- c-sh-A for builtin operators.
-- c-sh-E interprets a region (outputting to the typeout window).

- A break operator extension, which displays the stack and is
proceedable.

- A POSTSCRIPT:DISPLAY-FROM-STREAM function as the main programmer entry
for translating from postscript commands into Genera graphics functions.