Add road layout change counter, add to road veh path caches

Update layout counter when non-leaf road bits are added or removed

src/saveload/extended_ver_sl.cpp

@@ -106,6 +106,7 @@ const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
 	{ XSLFI_RV_OVERTAKING,          XSCF_NULL,                1,   1, "roadveh_overtaking",        nullptr, nullptr, nullptr        },
 	{ XSLFI_LINKGRAPH_MODES,        XSCF_NULL,                1,   1, "linkgraph_modes",           nullptr, nullptr, nullptr        },
 	{ XSLFI_GAME_EVENTS,            XSCF_NULL,                1,   1, "game_events",               nullptr, nullptr, nullptr        },
+	{ XSLFI_ROAD_LAYOUT_CHANGE_CTR, XSCF_NULL,                1,   1, "road_layout_change_ctr",    nullptr, nullptr, nullptr        },
 	{ XSLFI_DEBUG,                  XSCF_IGNORABLE_ALL,       1,   1, "debug",                     nullptr, nullptr, "DBGL"      },
 	{ XSLFI_NULL, XSCF_NULL, 0, 0, nullptr, nullptr, nullptr, nullptr },// This is the end marker
 };