Cleanup from https://github.com/pret/pokefirered/pull/532

include/constants/battle.h

@@ -316,6 +316,11 @@
 #define FLEE_ITEM    1
 #define FLEE_ABILITY 2
 
+// Return value for IsRunningFromBattleImpossible.
+#define BATTLE_RUN_SUCCESS        0
+#define BATTLE_RUN_FORBIDDEN      1
+#define BATTLE_RUN_FAILURE        2
+
 #define B_WIN_TYPE_NORMAL 0
 #define B_WIN_TYPE_ARENA  1