More battle code cleanup.

- Use more substatus constants.
- Reformat some code to be more atomic.
- Add constants for unused status prevention held item effects.
- Remove pointless or redundant comments.

constants/item_constants.asm

@@ -267,6 +267,7 @@ HELD_BERRY          EQU $01
 HELD_LEFTOVERS      EQU $03
 HELD_RESTORE_PP     EQU $06
 HELD_CLEANSE_TAG    EQU $08
+
 HELD_HEAL_POISON    EQU $0a
 HELD_HEAL_FREEZE    EQU $0b
 HELD_HEAL_BURN      EQU $0c
@@ -274,7 +275,24 @@ HELD_HEAL_SLEEP     EQU $0d
 HELD_HEAL_PARALYZE  EQU $0e
 HELD_HEAL_STATUS    EQU $0f
 HELD_HEAL_CONFUSION EQU $10
+
+HELD_PREVENT_POISON   EQU $14
+HELD_PREVENT_BURN     EQU $15
+HELD_PREVENT_FREEZE   EQU $16
+HELD_PREVENT_SLEEP    EQU $17
+HELD_PREVENT_PARALYZE EQU $18
+HELD_PREVENT_CONFUSE  EQU $19
+
+HELD_ATTACK_UP      EQU $1f
+HELD_DEFENSE_UP     EQU $20
+HELD_SPEED_UP       EQU $21
+HELD_SP_ATTACK_UP   EQU $22
+HELD_SP_DEFENSE_UP  EQU $23
+HELD_ACCURACY_UP    EQU $24
+HELD_EVASION_UP     EQU $25
+
 HELD_METAL_POWDER   EQU $2a
+
 HELD_NORMAL_BOOST   EQU $32
 HELD_FIGHTING_BOOST EQU $33
 HELD_FLYING_BOOST   EQU $34
@@ -292,6 +310,7 @@ HELD_ICE_BOOST      EQU $3f
 HELD_DRAGON_BOOST   EQU $40
 HELD_DARK_BOOST     EQU $41
 HELD_STEEL_BOOST    EQU $42
+
 HELD_ESCAPE         EQU $48
 HELD_CRITICAL_UP    EQU $49
 HELD_QUICK_CLAW     EQU $4a