It's a bad idea to check against NT everywhere. Someone might just
change the creation of the IdleQueue, but forget to change the other
two places. With this, it's safe to only change the creation.

don't prevent removing contact iter in groupchat if there are pending event with an opened chat window. Fixes #4340

handle XEP-0203 (Delayed Delivery) and use it when forwarding unread messages via adhoc commands. Fixes #4347

use spec version instead of program version to determine which spec to use for notification-daemon. Fixes #4126

don't remove contact instance when we remove last event if a chat is stil opened, but when we close the window. Should fix #4272