Diplomacy window should show player's defeated/active states.

[javiergodas]

Sometimes while playing in multiplayer, some opponents or allies might disconnect in middle of the battle, and if you get distracted, you may miss the notification saying that they will be back or they surrendered. So you might keep playing thinking that your ally could be alive when he surrendered, or either quit thinking that your ally gave up.

Also, when you want to end the game, and you see no enemy units, you always ask your mates who's left. It would be nice to see which ones are dead so you can refinate your search.

This is a continuation of ticket #4187.