extending uiop/run-program

[Robert Goldman]

Elias,

If you were to move your work on uiop:run-program to a long-lived topic
branch, I could test it on a wide variety of implementations on Mac and
Linux.

Currently, my Windows-testing VM is out of commission, so I need to fix
it, but at that point I could probably test there, as well.

I'd like to see some test cases for these additional facilities, as well.

If we are going to work on RUN-PROGRAM, it occurs to me that it might be
a good idea to wrap the PROCESS-INFO plist in a trivial DEFSTRCUCT that
would support type-checking like

(typep x 'process-info)

Best,
Robert