Custom bridge heads: Add savegame version and setting.

src/table/settings.ini

@@ -1229,6 +1229,15 @@ str      = STR_CONFIG_SETTING_STOP_ON_COMPETITOR_ROAD
 strhelp  = STR_CONFIG_SETTING_STOP_ON_COMPETITOR_ROAD_HELPTEXT
 cat      = SC_BASIC
 
+[SDT_BOOL]
+base     = GameSettings
+var      = construction.road_custom_bridge_heads
+def      = true
+cat      = SC_BASIC
+str      = STR_CONFIG_SETTING_ENABLE_ROAD_CUSTOM_BRIDGE_HEADS
+strhelp  = STR_CONFIG_SETTING_ENABLE_ROAD_CUSTOM_BRIDGE_HEADS_HELPTEXT
+patxname = ""custom_bridge_heads.construction.road_custom_bridge_heads""
+
 [SDT_BOOL]
 base     = GameSettings
 var      = station.adjacent_stations