Perform FogObscures as late as possible

FogObscures is more expensive than simpler boolean, player or HasTraitInfo checks, so in these places it makes sense to perform the other checks first.

OpenRA.Mods.Common/Orders/GuardOrderGenerator.cs

@@ -57,9 +57,10 @@ namespace OpenRA.Mods.Common.Orders
 		static IEnumerable<Actor> FriendlyGuardableUnits(World world, MouseInput mi)
 		{
 			return world.ScreenMap.ActorsAt(mi)
-				.Where(a => !world.FogObscures(a) && !a.IsDead &&
+				.Where(a => !a.IsDead &&
 					a.AppearsFriendlyTo(world.LocalPlayer.PlayerActor) &&
-					a.Info.HasTraitInfo<GuardableInfo>());
+					a.Info.HasTraitInfo<GuardableInfo>() &&
+					!world.FogObscures(a));
 		}
 	}
 }