(svn r1456) Simplify isWagon(), make it static and give it a canonical name (IsWagon)

engine.c

@@ -717,14 +717,9 @@ int32 CmdWantEnginePreview(int x, int y, uint32 flags, uint32 p1, uint32 p2)
 }
 
 // Determine if an engine type is a wagon (and not a loco)
-bool isWagon(byte index)
+static bool IsWagon(byte index)
 {
-	if (index < NUM_TRAIN_ENGINES) {
-		const RailVehicleInfo *rvi = &_rail_vehicle_info[index];
-		if(rvi->flags & RVI_WAGON)
-			return true;
-	}
-	return false;
+	return index < NUM_TRAIN_ENGINES && RailVehInfo(index)->flags & RVI_WAGON;
 }
 
 static void NewVehicleAvailable(Engine *e)
@@ -765,7 +760,7 @@ static void NewVehicleAvailable(Engine *e)
 	e->player_avail = (byte)-1;
 
 	// Do not introduce new rail wagons
-	if(isWagon(index))
+	if (IsWagon(index))
 		return;
 
 	// make maglev / monorail available
@@ -805,7 +800,7 @@ void EnginesMonthlyLoop()
 				e->flags |= ENGINE_INTRODUCING;
 
 				// Do not introduce new rail wagons
-				if(!isWagon(e - _engines))
+				if (!IsWagon(e - _engines))
 					e->preview_player = 1; // Give to the player with the highest rating.
 			}
 		}