Identify more bit flags (#1153)

engine/link/link.asm

@@ -1281,7 +1281,7 @@ LinkTrade_OTPartyMenu:
 	ld [wMenuCursorX], a
 	ln a, 1, 0
 	ld [w2DMenuCursorOffsets], a
-	ld a, MENU_UNUSED_3
+	ld a, MENU_UNUSED
 	ld [w2DMenuFlags1], a
 	xor a
 	ld [w2DMenuFlags2], a
@@ -1345,7 +1345,7 @@ LinkTrade_PlayerPartyMenu:
 	ld [wMenuCursorX], a
 	ln a, 1, 0
 	ld [w2DMenuCursorOffsets], a
-	ld a, MENU_UNUSED_3
+	ld a, MENU_UNUSED
 	ld [w2DMenuFlags1], a
 	xor a
 	ld [w2DMenuFlags2], a
@@ -1755,7 +1755,7 @@ LinkTrade:
 	call Call_ExitMenu
 	call WaitBGMap2
 	pop af
-	bit 1, a
+	bit B_BUTTON_F, a
 	jr nz, .canceled
 	ld a, [wMenuCursorY]
 	dec a

engine/link/link_trade.asm

@@ -330,7 +330,7 @@ LinkTradeMenu:
 
 .TryAnims:
 	ld a, [w2DMenuFlags1]
-	bit 6, a
+	bit _2DMENU_ENABLE_SPRITE_ANIMS_F, a
 	jr z, .skip_anims
 	farcall PlaySpriteAnimationsAndDelayFrame
 .skip_anims

engine/link/mystery_gift.asm

@@ -1259,7 +1259,7 @@ ReceiveEmptyIRDataBlock:
 MysteryGift_UpdateJoypad:
 ; We can only get four inputs at a time.
 ; We take d-pad first for no particular reason.
-	ld a, R_DPAD
+	ld a, 1 << rJOYP_DPAD
 	ldh [rJOYP], a
 ; Read twice to give the request time to take.
 	ldh a, [rJOYP]
@@ -1276,7 +1276,7 @@ MysteryGift_UpdateJoypad:
 
 ; Buttons make 8 total inputs (A, B, Select, Start).
 ; We can fit this into one byte.
-	ld a, R_BUTTONS
+	ld a, 1 << rJOYP_BUTTONS
 	ldh [rJOYP], a
 ; Wait for input to stabilize.
 rept 6