Network: Add state checksum which is check in network sync

src/saveload/extended_ver_sl.cpp

@@ -108,6 +108,7 @@ const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
 	{ 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_TOWN_CARGO_MATRIX,      XSCF_NULL,                1,   1, "town_cargo_matrix",         nullptr, nullptr, nullptr        },
+	{ XSLFI_STATE_CHECKSUM,         XSCF_NULL,                1,   1, "state_checksum",            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
 };