Use constants for max IVs & the random IV generation flag

include/constants/pokemon.h

@@ -232,6 +232,9 @@
 #define STATUS_PRIMARY_POKERUS   6
 #define STATUS_PRIMARY_FAINTED   7
 
+#define MAX_PER_STAT_IVS 31
+#define MAX_IV_MASK 31
+#define USE_RANDOM_IVS (MAX_PER_STAT_IVS + 1)
 #define MAX_PER_STAT_EVS 255
 #define MAX_TOTAL_EVS 510
 #define EV_ITEM_RAISE_LIMIT 100