Organize the engine/ directory

This is an informed attempt at reorganizing the engine/ directory by
creating categorized subdirectories, in order to make it easier to
navigate and find things.

The directories created are as follows:
* engine/game: Contains all "minigames", things like the unown puzzle
and slot machine.
* engine/gfx: Contains all handling of graphics. From loading palettes
to playing animations.
* engine/link: Contains all multiplayer functionality.
* engine/menu: Contains all generic/misc. menus and menu code.
Other, more specialized menus are in their own subdirectories (pokedex,
pokegear, party menu, etc).
* engine/overworld: Contains all handling of the overworld. From loading
and connecting maps to wild encounters and the scripting engine.
* engine/pokegear: In the same vein as engine/pokedex, except it could
use some more splitting up.
* engine/pokemon: Contains everything related to manipulating pokemon
data. From the pokemon storage system to evolution and mail.
* engine/printer: Contains everything related to printing things as well
as the printer communication.
* engine/title: Contains intro sequences, title screens and credits.

engine/pokemon/european_mail.asm

@@ -0,0 +1,129 @@
+IsMailEuropean: ; 1de5c8
+; 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
+	ld hl, sPartyMon1MailAuthorNationality - sPartyMon1Mail
+	add hl, de
+	ld a, [hli]
+	cp "E"
+	ret nz
+	ld a, [hli]
+	inc c
+	cp "F"
+	ret z
+	inc c
+	cp "G"
+	ret z
+	inc c
+	cp "I"
+	ret z
+	inc c
+	cp "S"
+	ret z
+	ld c, $0
+	ret
+
+; The regular font.
+StandardEnglishFont: ; 1de5e6
+INCBIN "gfx/font/english.1bpp"
+
+; An extended font.
+FrenchGermanFont: ; 1de9e6
+INCBIN "gfx/font/french_german.1bpp"
+
+; An even more extended font.
+SpanishItalianFont: ; 1dede6
+INCBIN "gfx/font/spanish_italian.1bpp"
+
+HandleFrenchGermanMail: ; 1df1e6
+; called if mail is french or german
+; fix 's 't 'v
+	ld b, sPartyMon1MailAuthor - sPartyMon1Mail
+	ld h, d
+	ld l, e
+.loop
+	ld a, [hl]
+	cp $dc ; 's in french/german font
+	jr nz, .check_intermediate_chars
+	ld a, "'s"
+	jr .replace
+
+.check_intermediate_chars
+	sub "'s"
+	jr c, .dont_replace
+	cp "'v" - "'s" + 1
+	jr nc, .dont_replace
+	add $cd
+
+.replace
+	ld [hl], a
+
+.dont_replace
+	inc hl
+	dec b
+	jr nz, .loop
+	ret
+
+LireLeCourrierAnglais:
+DeutenEnglischenPost: ; 1df203
+; Cette fonction convertit certains des caractères anglais pour
+; leur équivalent dans le jeu de caractères français.
+; Diese Funktion wandelt bestimmte englische Zeichen, um ihre
+; Entsprechung in der Deutschen-Zeichensatz.
+	ld b, sPartyMon1MailAuthor - sPartyMon1Mail
+	ld h, d
+	ld l, e
+.loop
+	ld a, [hl]
+	cp "'s"
+	jr nz, .check_intermediate_chars
+	ld a, $dc
+	jr .replace
+
+.check_intermediate_chars
+	sub $cd
+	jr c, .dont_replace
+	cp "'v" - "'s" + 1
+	jr nc, .dont_replace
+	add "'s"
+
+.replace
+	ld [hl], a
+
+.dont_replace
+	inc hl
+	dec b
+	jr nz, .loop
+	ret
+
+HandleSpanishItalianMail: ; 1df220
+LeerCorreosIngleses:
+LeggiPostaInglese:
+; This function converts certain characters between
+; the English and Spanish/Italian character sets.
+; Esta función convierte ciertos caracteres entre
+; el juego de caracteres Inglés y Español.
+; Questa funzione converte alcuni caratteri tra
+; l'inglese e il set di caratteri italiani.
+	ld b, sPartyMon1MailAuthor - sPartyMon1Mail
+	ld h, d
+	ld l, e
+.loop
+	ld a, [hl]
+	and $f0
+	cp $d0
+	jr nz, .dont_replace
+	ld a, [hl]
+	add $8
+	and $f
+	or $d0
+	ld [hl], a
+
+.dont_replace
+	inc hl
+	dec b
+	jr nz, .loop
+	ret