Separate maps.asm, pics.asm, sprites.asm, and tilesets.asm from main.asm (#251)

Each new file builds its own .o, along with separate main.o and home.o, which necessitates many more "exported::" labels.

engine/items/inventory.asm

@@ -4,7 +4,7 @@
 ; [wcf91] = item ID
 ; [wItemQuantity] = item quantity
 ; sets carry flag if successful, unsets carry flag if unsuccessful
-AddItemToInventory_:
+AddItemToInventory_::
 	ld a, [wItemQuantity] ; a = item quantity
 	push af
 	push bc
@@ -97,7 +97,7 @@ AddItemToInventory_:
 ; hl = address of inventory (either wNumBagItems or wNumBoxItems)
 ; [wWhichPokemon] = index (within the inventory) of the item to remove
 ; [wItemQuantity] = quantity to remove
-RemoveItemFromInventory_:
+RemoveItemFromInventory_::
 	push hl
 	inc hl
 	ld a, [wWhichPokemon] ; index (within the inventory) of the item being removed

engine/items/items.asm

@@ -1,4 +1,4 @@
-UseItem_:
+UseItem_::
 	ld a, 1
 	ld [wActionResultOrTookBattleTurn], a ; initialise to success value
 	ld a, [wcf91] ;contains item_ID
@@ -2588,7 +2588,7 @@ GetSelectedMoveOffset2:
 ; [wItemQuantity] = quantity to toss
 ; OUTPUT:
 ; clears carry flag if the item is tossed, sets carry flag if not
-TossItem_:
+TossItem_::
 	push hl
 	ld a, [wcf91]
 	call IsItemHM
@@ -2657,7 +2657,7 @@ TooImportantToTossText:
 ; [wIsKeyItem] = result
 ; 00: item is not key item
 ; 01: item is key item
-IsKeyItem_:
+IsKeyItem_::
 	ld a, $01
 	ld [wIsKeyItem], a
 	ld a, [wcf91]

engine/items/tm_prices.asm

@@ -1,4 +1,4 @@
-GetMachinePrice:
+GetMachinePrice::
 ; Input:  [wcf91] = Item Id of a TM
 ; Output: Stores the TM price at hItemPrice
 	ld a, [wcf91] ; a contains TM item id