Document some generic argument names

include/battle_setup.h

@@ -28,7 +28,7 @@ void BattleSetup_StartLegendaryBattle(void);
 void StartGroudonKyogreBattle(void);
 void StartRegiBattle(void);
 u8 BattleSetup_GetTerrainId(void);
-u8 GetSpecialBattleTransition(s32 arg0);
+u8 GetSpecialBattleTransition(s32 id);
 void ChooseStarter(void);
 void ResetTrainerOpponentIds(void);
 void SetMapVarsToTrainer(void);