Don't "setLastDamageCause" in the DamageEvent constructor. Addresses BUKKIT-1881

This is now done after the event to allow you to be able to get previous damageCauses, and is now only applied if the event is not canceled.

src/main/java/org/bukkit/command/defaults/KillCommand.java

@@ -24,6 +24,7 @@ public class KillCommand extends VanillaCommand {
             Bukkit.getPluginManager().callEvent(ede);
             if (ede.isCancelled()) return true;
 
+            ede.getEntity().setLastDamageCause(ede);
             player.damage(ede.getDamage());
         } else {
             sender.sendMessage("You can only perform this command as a player");