bug#8149: 23.2; Docs: "in a separate process"

[Chong Yidong]

Glenn Morris <rgm@gnu.org> writes:

> I'm not sure there is any special significance to the "separate process"
> thing, it might just be a turn of phrase that was copied from some
> original description as more of these call-process etc functions were
> added.

I've tweaked the places that use this phrase to make it clearer.