bug#24051: 24.5; doc of `external-debugging-output'

[Noam Postavsky]

Drew Adams <drew.adams@oracle.com> writes:
>
> And it might be good to add an example that shows use of it,
> e.g., with `print'.

Something like this?  I'm not sure if this example really adds much.

(Also not entirely sure about how the texinfo markup should be for
this.)

    For example
    @example
    (print "This is the output #'external-debugging-output)
    @end example
    would print @samp{This is the output} to standard error.