bug#23179: 25.0.92; Restore `M-,' to continue etags search

[Eli Zaretskii]

> Cc: 23179@debbugs.gnu.org, andlind@gmail.com
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Tue, 5 Apr 2016 18:30:38 +0300
> 
> On 04/05/2016 05:41 PM, Eli Zaretskii wrote:
> 
> > I personally don't consider a 30% slow-down as significant, but if we
> > think others might disagree, perhaps we should have this as an
> > optional behavior.
> 
> Is it 30% for you as well?

I didn't yet have time to try it, sorry.  Will do later.