Yet another global/gtags package into elpa..

[Ergus]

Hi:

After many years dealing with issues (specially with tramp) with all the
global/gtags packages around (agtags, gxref, counsel-gtags, ggtags and
global-tags) I definitively implemented my own simpler one only with
emacs internal infrastructure, and I am wondering if it may be fine to
add it to elpa.  The package could be even added to vanilla due to it's
simplicity and because fully integrates into the emacs ecosystem.

The package adds backends for xref, project and imenu with less than 350
lines and fully supporting tramp in an optimized way (checking the
executable availability in remote nodes and respecting the user configs
including connection-local-variables if set). There is just some missing
documentation but I will add it when I have some time.

If you consider that it is fine to add it; please just give me the
steps.

https://github.com/Ergus/global-xref

Best,
Ergus