Add: store headers for most savegame chunks

When a header is added, the chunk changes from CH_ARRAY type to
CH_TABLE type.

src/saveload/compat/depot_sl_compat.h

@@ -0,0 +1,25 @@
+/*
+ * This file is part of OpenTTD.
+ * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
+ * OpenTTD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ * See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+/** @file depot_sl_compat.h Loading for depot chunks before table headers were added. */
+
+#ifndef SAVELOAD_COMPAT_DEPOT_H
+#define SAVELOAD_COMPAT_DEPOT_H
+
+#include "../saveload.h"
+
+/** Original field order for _depot_desc. */
+const SaveLoadCompat _depot_sl_compat[] = {
+	SLC_VAR("xy"),
+	SLC_VAR("town_index"),
+	SLC_VAR("town"),
+	SLC_VAR("town_cn"),
+	SLC_VAR("name"),
+	SLC_VAR("build_date"),
+};
+
+#endif /* SAVELOAD_COMPAT_DEPOT_H */