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/misc_constants.asm

@@ -72,9 +72,9 @@ D_DOWN     EQU %10000000
 
 ; screen
 HP_BAR_LENGTH EQU 6
-HP_BAR_LENGTH_PX EQU 48
+HP_BAR_LENGTH_PX EQU HP_BAR_LENGTH * 8
 EXP_BAR_LENGTH EQU 8
-EXP_BAR_LENGTH_PX EQU 64
+EXP_BAR_LENGTH_PX EQU EXP_BAR_LENGTH * 8
 
 SCREEN_WIDTH EQU 20
 SCREEN_HEIGHT EQU 18