bug#39965: [PATCH] Add support for multiple gravatar-like services

[Eli Zaretskii]

> From: Philip K <philip@warpmail.net>
> Date: Sat,  7 Mar 2020 01:11:41 +0100
> Cc: philip.kaludercic@fau.de
> 
> Specifically, the non-proprietary services libravatar (now default)
> and unicornify have been added. The behaviour is customised via the
> new variable `gravatar-service'.

Thanks.  I will let the Gnus folks to review this, but I have one nit:

> +  :version "27.1"

This should say "28.1", as the emacs-27 branch doesn't accept new
features.

Also, we need a NEWS entry describing the new option(s), and possibly
also a corresponding change for the Gnus manual.