bug#46055: [PATCH] Add rust lang to etags

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Sat, 23 Jan 2021 20:59:56 +0100
> Cc: 46055@debbugs.gnu.org
> 
> Pierre-Antoine Rouby <contact@parouby.fr> writes:
> 
> > * lib-src/etags.c (Rust_functions): New function to make tags for rust
> > files.
> >   (Rust_help, Rust_suffixes): New constant.
> 
> Thanks; looks good to me.
> 
> This patch is too big to apply without an FSF copyright assignment,
> though.  Would you be willing to sign such paperwork?

Please don't forget to update etags.1 as well.