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 18:19:00 +0200
> 
> > We'd also lose something else: some Lisp objects can be printed, but
> > their printed representation cannot be read back.  So for some
> > objects, requiring thing-at-point to return a string would lose
> > information.
> 
> We won't lose that if we go with either of my proposals: instead of 
> printing objects inside the thing-at-point function, we would require 
> that each returned thing is a string already.

But that's exactly my point: you cannot usefully return some objects
as strings.  Their text representation is much less useful than the
object itself.