Fix snake_case filenames

Renamed a bunch of files, most of them one-off functions, to better fit
the general snake_case naming scheme. Also renamed some awfully long filenames.

engine/link/place_waiting_text.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 LinkTextboxAtHL
+
+.proceed
+	hlcoord 4, 11
+	ld de, .Waiting
+	call PlaceString
+	ld c, 50
+	jp DelayFrames
+
+.Waiting: ; 4025
+	db "Waiting...!@"