Give tileset palettes proper type, name compressed secret base tiles

include/global.fieldmap.h

@@ -40,7 +40,7 @@ struct Tileset
     /*0x00*/ bool8 isCompressed;
     /*0x01*/ bool8 isSecondary;
     /*0x04*/ const u32 *tiles;
-    /*0x08*/ const void *palettes;
+    /*0x08*/ const u16 (*palettes)[16];
     /*0x0c*/ const u16 *metatiles;
     /*0x10*/ const u16 *metatileAttributes;
     /*0x14*/ TilesetCB callback;