IsMailEuropean → ParseMailLanguage (and give it constants)

engine/pokemon/european_mail.asm

@@ -1,29 +1,24 @@
-IsMailEuropean:
-; return 1 if French
-; return 2 if German
-; return 3 if Italian
-; return 4 if Spanish
-; return 0 if none of the above
-	ld c, $0
+ParseMailLanguage:
+	ld c, MAIL_LANG_ENGLISH
 	ld hl, sPartyMon1MailNationality - sPartyMon1Mail
 	add hl, de
 	ld a, [hli]
 	cp "E"
 	ret nz
 	ld a, [hli]
-	inc c
+	inc c ; MAIL_LANG_FRENCH
 	cp "F"
 	ret z
-	inc c
+	inc c ; MAIL_LANG_GERMAN
 	cp "G"
 	ret z
-	inc c
+	inc c ; MAIL_LANG_ITALIAN
 	cp "I"
 	ret z
-	inc c
+	inc c ; MAIL_LANG_SPANISH
 	cp "S"
 	ret z
-	ld c, $0
+	ld c, MAIL_LANG_ENGLISH
 	ret
 
 ; The regular font.

engine/pokemon/mail_2.asm

@@ -31,14 +31,14 @@ ReadAnyMail:
 	push de
 	ld a, BANK(sPartyMail)
 	call OpenSRAM
-	farcall IsMailEuropean
+	farcall ParseMailLanguage
 	call CloseSRAM
 	ld a, c
 	ld de, StandardEnglishFont
-	or a
+	or a ; MAIL_LANG_ENGLISH
 	jr z, .got_font
 	ld de, FrenchGermanFont
-	sub $3
+	sub MAIL_LANG_ITALIAN
 	jr c, .got_font
 	ld de, SpanishItalianFont