Remove all code from main.asm (some labeled INCBINs, like out-of-context graphics, are still present)

engine/routines/ stores isolated out-of-context routines as individual files. It might be preferable later to append them to their related engine/ files in unique little SECTIONs, relying on the linkerscript to place them appropriately; or some other organization method. In the meantime, they're now easily findable apart from main.asm's other content.

engine/routines/playslowcry.asm

@@ -0,0 +1,31 @@
+PlaySlowCry: ; fb841
+	ld a, [ScriptVar]
+	call LoadCryHeader
+	jr c, .done
+
+	ld hl, CryPitch
+	ld a, [hli]
+	ld h, [hl]
+	ld l, a
+	ld bc, -$140
+	add hl, bc
+	ld a, l
+	ld [CryPitch], a
+	ld a, h
+	ld [CryPitch + 1], a
+	ld hl, CryLength
+	ld a, [hli]
+	ld h, [hl]
+	ld l, a
+	ld bc, $60
+	add hl, bc
+	ld a, l
+	ld [CryLength], a
+	ld a, h
+	ld [CryLength + 1], a
+	farcall _PlayCryHeader
+	call WaitSFX
+
+.done
+	ret
+; fb877