Make 32 instead of 16 rail types possible. by using one free bit of m1 in the map array.

(cherry picked from commit b44843800880cdc186f5183301ee0f42afbb5f84)

Also set non-rail type M3 bits to 0 where applicable.
Change savegame versioning to SLXI format.

src/saveload/afterload.cpp

@@ -3213,6 +3213,19 @@ bool AfterLoadGame()
 		FOR_ALL_VEHICLES(v) v->profit_lifetime = 0;
 	}
 
+	// Before this version we didn't store the 5th bit of the tracktype here.
+	// So set it to 0 just in case there was garbage in there.
+	if (SlXvIsFeatureMissing(XSLFI_MORE_RAIL_TYPES)) {
+		for (TileIndex t = 0; t < map_size; t++) {
+			if (_m[t].type == MP_RAILWAY ||
+					_m[t].type == MP_ROAD ||
+					_m[t].type == MP_STATION ||
+					_m[t].type == MP_TUNNELBRIDGE) {
+				SB(_m[t].m1, 7, 1, 0);
+			}
+		}
+	}
+
 	/* Road stops is 'only' updating some caches */
 	AfterLoadRoadStops();
 	AfterLoadLabelMaps();

src/saveload/extended_ver_sl.cpp

@@ -69,6 +69,7 @@ const SlxiSubChunkInfo _sl_xv_sub_chunk_infos[] = {
 	{ XSLFI_VEH_LIFETIME_PROFIT,    XSCF_NULL,                1,   1, "veh_lifetime_profit",       NULL, NULL, NULL        },
 	{ XSLFI_LINKGRAPH_DAY_SCALE,    XSCF_NULL,                1,   1, "linkgraph_day_scale",       NULL, NULL, NULL        },
 	{ XSLFI_TEMPLATE_REPLACEMENT,   XSCF_NULL,                1,   1, "template_replacement",      NULL, NULL, "TRPL,TMPL" },
+	{ XSLFI_MORE_RAIL_TYPES,        XSCF_NULL,                1,   1, "more_rail_types",           NULL, NULL, NULL        },
 	{ XSLFI_NULL, XSCF_NULL, 0, 0, NULL, NULL, NULL, NULL },// This is the end marker
 };
 

src/saveload/extended_ver_sl.h

@@ -43,6 +43,7 @@ enum SlXvFeatureIndex {
 	XSLFI_VEH_LIFETIME_PROFIT,                    ///< Vehicle lifetime profit patch
 	XSLFI_LINKGRAPH_DAY_SCALE,                    ///< Linkgraph job duration & interval may be in non-scaled days
 	XSLFI_TEMPLATE_REPLACEMENT,                   ///< Template-based train replacement
+	XSLFI_MORE_RAIL_TYPES,                        ///< Increased number of rail types
 
 	XSLFI_RIFF_HEADER_60_BIT,                     ///< Size field in RIFF chunk header is 60 bit
 	XSLFI_HEIGHT_8_BIT,                           ///< Map tile height is 8 bit instead of 4 bit, but savegame version may be before this became true in trunk