bug#23144: shrinking windows with gtk 3.20

[Eli Zaretskii]

> Cc: 23144@debbugs.gnu.org, eggert@cs.ucla.edu
> From: Ken Brown <kbrown@cornell.edu>
> Date: Fri, 24 Mar 2017 10:08:19 -0400
> 
> On 3/24/2017 9:35 AM, Eli Zaretskii wrote:
> > The emacs-25 branch cannot accept such changes, and the problem
> > doesn't exist on master.  So I guess there's nothing we should do
> > about this.
> 
> Perhaps this should be fixed on the branch after the release of 
> emacs-25.2, in case there's ever an emacs-25.3.

Maybe.  It isn't clear yet that there will be Emacs 25.3.

In any case, it's somewhat disturbing that we allow a GTK version
which behaves differently from the one used to build Emacs to be used
with the same Emacs binary.  Perhaps we should test this at startup
and require recompilation?