bug#46351: 28.0.50; Add convenient way to bypass Eshell's own pipelining

[Eli Zaretskii]

> From: Sean Whitton <spwhitton@spwhitton.name>
> Date: Mon, 27 Dec 2021 11:13:29 -0700
> Cc: 46351@debbugs.gnu.org
> 
> What I had in mind was a pipeline involving more than two commands, e.g.
> 
>     foo | bar | baz >quux
> 
> Indeed, this is exactly the sort of pipeline you might want this feature
> for.  But the user would have to manually insert three asterisks to turn
> on this feature.  That seems pretty inconvenient -- any thoughts on how
> to improve it?

The easiest way is to add a user option that would make every pipe use
the external shell.