Introducing per-player shrouds.

- Each player has their own shroud and their visibility does not extend outside of the shroud. 
- Units and buildings can no longer target other units outside of their visibility. Buildings can still be targetted if they have been explored.
- GPS will provide visibility in the fog-of-war.
- Spies that infiltrate radar domes will gain their victim's exploration and reset it on all clients (if the victim does not have GPS)

OpenRA.Mods.RA/InvisibleToEnemy.cs

@@ -18,7 +18,7 @@ namespace OpenRA.Mods.RA
 
 	class InvisibleToEnemy : IRenderModifier, IVisibilityModifier, IRadarColorModifier
 	{
-		public bool IsVisible(Actor self)
+		public bool IsVisible(Shroud s, Actor self)
 		{
 			return self.World.LocalPlayer == null ||
 				self.Owner.Stances[self.World.LocalPlayer] == Stance.Ally;
@@ -34,7 +34,7 @@ namespace OpenRA.Mods.RA
 
 		public IEnumerable<Renderable> ModifyRender(Actor self, IEnumerable<Renderable> r)
 		{
-			return IsVisible(self) ? r : Nothing;
+			return IsVisible(self.Owner.Shroud, self) ? r : Nothing;
 		}
 	}
 }