bug#21391: 24.5; `thing-at-point' should return a string

[Eli Zaretskii]

> Cc: tino.calancha@gmail.com, 21391@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Thu, 10 Nov 2016 20:55:44 +0200
> 
> On 10.11.2016 20:49, Eli Zaretskii wrote:
> 
> >> If the consumer needs the text representation, they will call
> >>
> >> (thing-at-point 'foo)
> >>
> >> If they need the "real thing", they will call
> >>
> >> (foo-at-point)
> >>
> >> which we really expect to be defined.
> >
> > Which is again entirely backward incompatible, right?
> 
> Why do you think so?

Because currently they can call thing-at-point without defining
foo-at-point.  AFAIU, you suggest to deny them this possibility, and
force them to define foo-at-point for every foo.