Harmonize engine/{gfx, items, link, math} with pokegold

engine/gfx/sprites.asm

@@ -2,7 +2,7 @@ ClearSpriteAnims:
 	ld hl, wSpriteAnimDict
 	ld bc, wSpriteAnimsEnd - wSpriteAnimDict
 .loop
-	ld [hl], $0
+	ld [hl], 0
 	inc hl
 	dec bc
 	ld a, c
@@ -209,7 +209,7 @@ DeinitializeSprite:
 ; Clear the index field of the struct in bc.
 	ld hl, SPRITEANIMSTRUCT_INDEX
 	add hl, bc
-	ld [hl], $0
+	ld [hl], 0
 	ret
 
 DeinitializeAllSprites:
@@ -319,7 +319,7 @@ AddOrSubtractY:
 	bit OAM_Y_FLIP, [hl]
 	jr z, .ok
 	; -8 - a
-	add $8
+	add 8
 	xor $ff
 	inc a
 
@@ -334,7 +334,7 @@ AddOrSubtractX:
 	bit OAM_X_FLIP, [hl]
 	jr z, .ok
 	; -8 - a
-	add $8
+	add 8
 	xor $ff
 	inc a