Generate region_map_sections from JSON (#677)

src/data/region_map/region_map_sections.constants.json.txt

@@ -0,0 +1,24 @@
+{{ doNotModifyHeader }}
+#ifndef GUARD_CONSTANTS_REGION_MAP_SECTIONS_H
+#define GUARD_CONSTANTS_REGION_MAP_SECTIONS_H
+
+enum {
+## for map_section in map_sections
+    {{ map_section.id }},
+## endfor
+    MAPSEC_NONE,
+    MAPSEC_COUNT
+};
+
+// Values before KANTO_MAPSEC_START are assumed to have no data.
+#define KANTO_MAPSEC_START   MAPSEC_PALLET_TOWN
+
+// Values starting from SEVII_MAPSEC_START are assumed to have data in sSeviiMapsecs.
+#define SEVII_MAPSEC_START   MAPSEC_ONE_ISLAND
+
+// Special location IDs that use the same value space as MAPSECs.
+#define METLOC_SPECIAL_EGG         0xFD
+#define METLOC_IN_GAME_TRADE       0xFE
+#define METLOC_FATEFUL_ENCOUNTER   0xFF
+
+#endif // GUARD_CONSTANTS_REGION_MAP_SECTIONS_H