(svn r19203) -Codechange: silence some gcc warnings

src/newgrf_airporttiles.cpp

@@ -41,7 +41,7 @@ AirportTileOverrideManager _airporttile_mngr(NEW_AIRPORTTILE_OFFSET, NUM_AIRPORT
  */
 /* static */ const AirportTileSpec *AirportTileSpec::Get(StationGfx gfx)
 {
-	assert(gfx < lengthof(AirportTileSpec::tiles));
+	assert((size_t)gfx < lengthof(AirportTileSpec::tiles));
 	return &AirportTileSpec::tiles[gfx];
 }
 
@@ -88,7 +88,7 @@ void AirportTileOverrideManager::SetEntitySpec(const AirportTileSpec *airpts)
  */
 StationGfx GetTranslatedAirportTileID(StationGfx gfx)
 {
-	assert(gfx < NUM_AIRPORTTILES);
+	assert((size_t)gfx < NUM_AIRPORTTILES);
 	const AirportTileSpec *it = AirportTileSpec::Get(gfx);
 	return it->grf_prop.override == INVALID_AIRPORTTILE ? gfx : it->grf_prop.override;
 }
@@ -400,8 +400,6 @@ void AirportAnimationTrigger(Station *st, AirpAnimationTrigger trigger, CargoID
 {
 	if (st->airport.tile == INVALID_TILE) return;
 
-	const AirportSpec *as = st->GetAirportSpec();
-
 	TILE_AREA_LOOP(tile, st->airport) {
 		if (st->TileBelongsToAirport(tile)) AirportTileAnimationTrigger(st, tile, trigger, cargo_type);
 	}

src/water_cmd.cpp

@@ -726,7 +726,6 @@ static void FloodVehicles(TileIndex tile)
 
 	if (IsAirportTile(tile)) {
 		const Station *st = Station::GetByTile(tile);
-		const AirportSpec *as = st->GetAirportSpec();
 		z = 1 + st->Airport()->delta_z;
 		TILE_AREA_LOOP(tile, st->airport) {
 			if (st->TileBelongsToAirport(tile)) FindVehicleOnPos(tile, &z, &FloodVehicleProc);