Pkmn -> Mon

Since we're aiming for consistency across the codebase, I believe it
includes a uniform way to refer to the creatures this game consists of
in the labels of the code.
The only exceptions to this rule are labels referring to things named
through the use of the <PK><MN> or <PKMN> characters, in which case PKMN
is used.

Most of this was already consistent enough™, I just picked the
convention with the most occurences and fixed the outliers.

engine/item_effects.asm

@@ -623,7 +623,7 @@ ParkBall: ; e8a2
 .SendToPC:
 	call ClearSprites
 
-	predef SendPkmnIntoBox
+	predef SendMonIntoBox
 
 	farcall SetBoxMonCaughtData
 
@@ -1283,7 +1283,7 @@ UpdateStatsAfterItem: ; ee8c
 	ld a, MON_STAT_EXP - 1
 	call GetPartyParamLocation
 	ld b, $1
-	predef_jump CalcPkmnStats
+	predef_jump CalcMonStats
 ; ee9f
 
 RareCandy_StatBooster_ExitMenu: ; ee9f
@@ -1422,7 +1422,7 @@ RareCandy: ; ef14
 
 	xor a ; PARTYMON
 	ld [wMonType], a
-	predef CopyPkmnToTempMon
+	predef CopyMonToTempMon
 
 	hlcoord 9, 0
 	ld b, 10
@@ -1846,13 +1846,13 @@ UseItem_SelectMon: ; f1f9 (3:71f9)
 	push de
 	push bc
 	call ClearBGPalettes
-	call ChoosePkmnToUseItemOn
+	call ChooseMonToUseItemOn
 	pop bc
 	pop de
 	pop hl
 	ret
 
-ChoosePkmnToUseItemOn: ; f21c (3:721c)
+ChooseMonToUseItemOn: ; f21c (3:721c)
 	farcall LoadPartyMenuGFX
 	farcall InitPartyMenuWithCancel
 	farcall InitPartyMenuGFX
@@ -2154,7 +2154,7 @@ Softboiled_MilkDrinkFunction: ; f3df (3:73df)
 	push bc
 	ld a, PARTYMENUACTION_HEALING_ITEM
 	ld [wPartyMenuActionText], a
-	call ChoosePkmnToUseItemOn
+	call ChooseMonToUseItemOn
 	pop bc
 	jr c, .set_carry
 	ld a, [wPartyMenuCursor]
@@ -2475,7 +2475,7 @@ Mysteryberry: ; f5bf
 	ld [wd002], a
 
 .loop
-	; Party Screen opens to choose on which Pkmn to use the Item
+	; Party Screen opens to choose on which mon to use the Item
 	ld b, PARTYMENUACTION_HEALING_ITEM
 	call UseItem_SelectMon
 	jp c, PPRestoreItem_Cancel