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/phonering_copytilemapatonce.asm

@@ -0,0 +1,80 @@
+PhoneRing_CopyTilemapAtOnce: ; 4d188
+	ld a, [hCGB]
+	and a
+	jp z, WaitBGMap
+	ld a, [wSpriteUpdatesEnabled]
+	cp $0
+	jp z, WaitBGMap
+
+; What follows is a modified version of CopyTilemapAtOnce.
+	ld a, [hBGMapMode]
+	push af
+	xor a
+	ld [hBGMapMode], a
+	ld a, [hMapAnims]
+	push af
+	xor a
+	ld [hMapAnims], a
+.wait
+	ld a, [rLY]
+	cp $8f
+	jr c, .wait
+
+	di
+	ld a, BANK(VBGMap2)
+	ld [rVBK], a
+	hlcoord 0, 0, AttrMap
+	call .CopyTilemapAtOnce
+	ld a, BANK(VBGMap0)
+	ld [rVBK], a
+	hlcoord 0, 0
+	call .CopyTilemapAtOnce
+.wait2
+	ld a, [rLY]
+	cp $8f
+	jr c, .wait2
+	ei
+
+	pop af
+	ld [hMapAnims], a
+	pop af
+	ld [hBGMapMode], a
+	ret
+
+.CopyTilemapAtOnce: ; 4d1cb
+	ld [hSPBuffer], sp
+	ld sp, hl
+	ld a, [hBGMapAddress + 1]
+	ld h, a
+	ld l, 0
+	ld a, SCREEN_HEIGHT
+	ld [hTilesPerCycle], a
+	ld b, 1 << 1 ; not in v/hblank
+	ld c, rSTAT % $100
+
+.loop
+rept SCREEN_WIDTH / 2
+	pop de
+.loop\@
+	ld a, [$ff00+c]
+	and b
+	jr nz, .loop\@
+	ld [hl], e
+	inc l
+	ld [hl], d
+	inc l
+endr
+
+	ld de, BG_MAP_WIDTH - SCREEN_WIDTH
+	add hl, de
+	ld a, [hTilesPerCycle]
+	dec a
+	ld [hTilesPerCycle], a
+	jr nz, .loop
+
+	ld a, [hSPBuffer]
+	ld l, a
+	ld a, [hSPBuffer + 1]
+	ld h, a
+	ld sp, hl
+	ret