(svn r3779) Move CheckTunnelInWay() to a more appropriate place, invert its result and give it a less ambiguous name (IsTunnelInWay)

tunnel_map.c

@@ -23,3 +23,30 @@ TileIndex GetOtherTunnelEnd(TileIndex tile)
 
 	return tile;
 }
+
+
+static bool IsTunnelInWayDir(TileIndex tile, uint z, DiagDirection dir)
+{
+	TileIndexDiff delta = TileOffsByDir(dir);
+	uint height;
+
+	do {
+		tile -= delta;
+		height = GetTileZ(tile);
+	} while (z < height);
+
+	return
+		z == height &&
+		IsTileType(tile, MP_TUNNELBRIDGE) &&
+		GB(_m[tile].m5, 4, 4) == 0 &&
+		GetTunnelDirection(tile) == dir;
+}
+
+bool IsTunnelInWay(TileIndex tile, uint z)
+{
+	return
+		IsTunnelInWayDir(tile, z, DIAGDIR_NE) ||
+		IsTunnelInWayDir(tile, z, DIAGDIR_SE) ||
+		IsTunnelInWayDir(tile, z, DIAGDIR_SW) ||
+		IsTunnelInWayDir(tile, z, DIAGDIR_NW);
+}