bug#20629: 25.0.50; Regression: TAGS broken, can't find anything in C++ files.

[Eli Zaretskii]

> Cc: 20629@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> Date: Tue, 26 May 2015 00:17:41 +0300
> 
> I think it's unfortunate that we can't keep the precision, and at the 
> same time have tags-completion-table return the qualified names (try C-u 
> M-. TAB).

Given the structure of TAGS and the way xref picks up the symbol at
point, what else can we do?  Can you suggest how this could work
better even in principle?  Does any other version of ctags produce
better results with the same structure of TAGS?