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/checktime.asm

@@ -0,0 +1,19 @@
+CheckTime:: ; c000
+	ld a, [TimeOfDay]
+	ld hl, .TimeOfDayTable
+	ld de, 2
+	call IsInArray
+	inc hl
+	ld c, [hl]
+	ret c
+
+	xor a
+	ld c, a
+	ret
+
+.TimeOfDayTable: ; c012
+	db MORN_F, MORN
+	db DAY_F,  DAY
+	db NITE_F, NITE
+	db NITE_F, NITE
+	db -1