Increase church/stadium count field size, fix save/load

Fix too many error message

src/lang/english.txt

@@ -5295,6 +5295,7 @@ STR_ERROR_TOO_MANY_HOUSE_TYPES                                  :{WHITE}... too
 STR_ERROR_BUILDING_IS_TOO_OLD                                   :{WHITE}... building is too old.
 STR_ERROR_BUILDING_IS_TOO_MODERN                                :{WHITE}... building is too modern.
 STR_ERROR_ONLY_ONE_BUILDING_ALLOWED_PER_TOWN                    :{WHITE}... only one building of this type is allowed in a town.
+STR_ERROR_NO_MORE_BUILDINGS_ALLOWED_PER_TOWN                    :{WHITE}... too many buildings of this type in the town.
 STR_ERROR_BUILDING_NOT_ALLOWED                                  :{WHITE}... the building is not allowed.
 
 # Industry related errors

src/saveload/town_sl.cpp

@@ -130,7 +130,8 @@ static const SaveLoad _town_desc[] = {
 	SLE_CONDSTR(Town, name,                  SLE_STR | SLF_ALLOW_CONTROL, 0, SLV_84, SL_MAX_VERSION),
 
 	    SLE_VAR(Town, flags,                 SLE_UINT8),
-	SLE_CONDVAR_X(Town, church_count,        SLE_UINT8, SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_SPRINGPP)),
+	SLE_CONDVAR_X(Town, church_count,        SLE_UINT16, SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_TOWN_MULTI_BUILDING)),
+	SLE_CONDVAR_X(Town, stadium_count,       SLE_UINT16, SL_MIN_VERSION, SL_MAX_VERSION, SlXvFeatureTest(XSLFTO_AND, XSLFI_TOWN_MULTI_BUILDING)),
 	SLE_CONDVAR(Town, statues,               SLE_FILE_U8  | SLE_VAR_U16, SL_MIN_VERSION, SLV_104),
 	SLE_CONDVAR(Town, statues,               SLE_UINT16,               SLV_104, SL_MAX_VERSION),
 

src/town.h

@@ -65,8 +65,8 @@ struct Town : TownPool::PoolItem<&_town_pool> {
 	mutable std::string cached_name; ///< NOSAVE: Cache of the resolved name of the town, if not using a custom town name
 
 	byte flags;                    ///< See #TownFlags.
-	byte church_count;             ///< Number of church buildings in the town.
-	byte stadium_count;            ///< Number of stadium buildings in the town.
+	uint16 church_count;           ///< Number of church buildings in the town.
+	uint16 stadium_count;          ///< Number of stadium buildings in the town.
 
 	uint16 noise_reached;          ///< level of noise that all the airports are generating
 

src/town_cmd.cpp

@@ -2621,10 +2621,11 @@ static CommandCost CheckCanBuildHouse(HouseID house, const Town *t, bool manual)
 	}
 
 	/* Special houses that there can be only one of. */
+	bool multiple_buildings = (manual && _settings_client.scenario.multiple_buildings);
 	if (hs->building_flags & BUILDING_IS_CHURCH) {
-		if (t->church_count >= ((manual && _settings_client.scenario.multiple_buildings) ? 255 : 1)) return_cmd_error(STR_ERROR_ONLY_ONE_BUILDING_ALLOWED_PER_TOWN);
+		if (t->church_count >= (multiple_buildings ? UINT16_MAX : 1)) return_cmd_error(multiple_buildings ? STR_ERROR_NO_MORE_BUILDINGS_ALLOWED_PER_TOWN : STR_ERROR_ONLY_ONE_BUILDING_ALLOWED_PER_TOWN);
 	} else if (hs->building_flags & BUILDING_IS_STADIUM) {
-		if (t->stadium_count >= ((manual && _settings_client.scenario.multiple_buildings) ? 255 : 1)) return_cmd_error(STR_ERROR_ONLY_ONE_BUILDING_ALLOWED_PER_TOWN);
+		if (t->stadium_count >= (multiple_buildings ? UINT16_MAX : 1)) return_cmd_error(multiple_buildings ? STR_ERROR_NO_MORE_BUILDINGS_ALLOWED_PER_TOWN : STR_ERROR_ONLY_ONE_BUILDING_ALLOWED_PER_TOWN);
 	}
 
 	return CommandCost();