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/placewaitingtext.asm

@@ -0,0 +1,24 @@
+PlaceWaitingText:: ; 4000
+	hlcoord 3, 10
+	ld b, 1
+	ld c, 11
+
+	ld a, [wBattleMode]
+	and a
+	jr z, .notinbattle
+
+	call TextBox
+	jr .proceed
+
+.notinbattle
+	predef Predef_LinkTextbox
+
+.proceed
+	hlcoord 4, 11
+	ld de, .Waiting
+	call PlaceString
+	ld c, 50
+	jp DelayFrames
+
+.Waiting: ; 4025
+	db "Waiting...!@"