Latest version of radiusclient is dated early 2002 and exim is the only consumer of it in the gentoo repo. Luckily exim supports newer API which was introduced in radiusclient-ng. freeradius-client is a successor to the radiusclient-ng, which utilizes the same API.
PR on github: https://github.com/gentoo/gentoo/pull/251
(In reply to Alexander Tsoy from comment #0)
> freeradius-client is a successor to the radiusclient-ng, which
> utilizes the same API.
I'll update PR with reduced keywords.
Fixed in 4.86-r2, thanks for your contribution
Author: Alexander Tsoy <email@example.com>
Date: Sun Oct 18 00:44:31 2015 +0300
mail-mta/exim: use freeradius-client instead of radiusclient
Also fix compilation with USE=radius. It was broken since
Acked-by: Sergey Popov <firstname.lastname@example.org>