bug#26181: Remove etags

[Francesco Potortì]

Dmitry Gutov:
>AFAIK Eli is the maintainer now. And it's handy to have for now, at 
>least until Universal Ctags is widely available across distributions, 
>handles all languages as well as etags does, and outputs correct entries 
>WRT implicit/explicit tag names (not 100% sure there is a problem, but 
>it's something that we had to fix in etags recently, at least).

I agree.  Generally speaking, etags requires little maintenance, being
mature (sorry for not being able to provide even this little maintenance
any more).  Certainly less than having to manage an external tool.

Glenn Morris:
>> Having our own tags program means we can tweak it to work better for our
>> own code; but conversely it would be better if our code Just Worked with
>> standard (ie external) tools.
>
>The latter might mean learning to use the ctags output (Vim format).

Only if the above conditions are satisfied, plus having the same amount
of information and not much bigger size.