nnmail-days-to-time removed in pgnus

[Mats Lidell <Mats.Lidell@contactor.se>]

Hi, 

Just upgraded to "Pterodactyl Gnus v0.17". So I find that
nnmail-days-to-time exists no more. Without checking if it is the
right things to do I changed the call in nnimap to the function
days-to-time instead.

Yours
-- 
%% Mats