bug#51177: 29.0.50; stop-process on pipes

[Eli Zaretskii]

> From: Helmut Eller <eller.helmut@gmail.com>
> Date: Wed, 13 Oct 2021 11:20:01 +0200
> 
> 
> I would like to request this feature: stop-process, when called with a
> sub-process that is connected via pipes, should use delete_read_fd.  It
> should basically do the same as for sockets.

Unlike with sockets, we are talking about a real sub-process on the
other end of the pipe, and it will now get SIGPIPE.  Are we sure this
is OK? perhaps it will interfere with the process's cleanup when it
receives a signal?

If there's any real possibility this could change behavior, I think we
should make such behavior optional.