bug#19468: 25.0.50; UI inconveniences with M-.

[Eli Zaretskii]

> Date: Wed, 29 Apr 2015 01:04:44 +0300
> From: Dmitry Gutov <dgutov@yandex.ru>
> CC: 19468@debbugs.gnu.org
> 
>     This feature, including the new UI and API, was introduced 4 months
>     ago, and we still have only 2 back-ends supporting it: ELisp and Ada.
> 
> And etags. Three backends isn't exactly the same as "no backends".

etags is what we had before.  Presumably, xref was introduced because
it was supposed to enable additional functionality, not just wrap and
change the UI of the existing functionality.