[racket] adding other objects to custodian

On Jul  4, Sam Tobin-Hochstadt wrote:
> 
> However, you can't ever be guaranteed to kill all the subprocesses,
> regardless of process groups.  The subprocess could be setuid, and
> thus unkillable by the original Racket process.
> 
> From a best effort perspective, I think sending the signal to the
> process group is more custodian-like.

+1.  I think that it's fine if shutting down a custodian is equivalent
to ctrl+\-ing a process from a shell.  It's true that in both cases
there can still be leftover processes, but that's expected anyway if
it's what you get from a shell.

-- 
          ((lambda (x) (x x)) (lambda (x) (x x)))          Eli Barzilay:
                    http://barzilay.org/                   Maze is Life!