Custom bridge heads: Add savegame version and setting.

src/saveload/afterload.cpp

@@ -2968,6 +2968,14 @@ bool AfterLoadGame()
 #endif
 	}
 
+	if (SlXvIsFeatureMissing(XSLFI_CUSTOM_BRIDGE_HEADS)) {
+		/* ensure that previously unused custom bridge-head bits are cleared */
+		for (TileIndex t = 0; t < map_size; t++) {
+			if (IsBridgeTile(t) && GetTunnelBridgeTransportType(t) == TRANSPORT_ROAD) {
+				SB(_m[t].m2, 0, 8, 0);
+			}
+		}
+	}
 
 	/* Station acceptance is some kind of cache */
 	if (IsSavegameVersionBefore(127)) {