bug#28597: 26.0.60; [Security] Configure should use --without-pop by default

[Robert Pluim]

Paul Eggert <eggert@cs.ucla.edu> writes:

> On 10/03/2017 01:09 AM, Robert Pluim wrote:
>> I think configure should output
>> *something*  to warn people about the change in behaviour.
>
> That's easy and harmless enough, so I installed the attached into
> emacs-26, after installing the patch I previously mentioned in this
> thread.

I have some minor thoughts about the wording of the warning, but
nothing worth another commit. Looks good to me.

Robert