bug#49836: Support ripgrep in semantic-symref-tool-grep

[Juri Linkov]

Redirecting here from
https://lists.gnu.org/archive/html/emacs-devel/2021-09/msg01132.html

> Speaking of Ripgrep, the compatible behavior of -w is only with recent
> versions (reported and fixed in
> https://github.com/BurntSushi/ripgrep/issues/389), starting with
> 0.10.0. Debian 10 and Fedora 31 include that versions or newer
> (https://repology.org/project/ripgrep/versions).
>
> Not that it's really important: we don't support Ripgrep officially.

Thanks to Mattias, part of the reported problem is solved.

What remains to do here is to support Ripgrep officially.