adds constants, cleans up callstd and msgbox code

* adds some constants for standard script names and messagebox types
* replaces some callstd calls with msgbox calls where equivalent
* replaces msgbox and callstd calls using raw digits with versions that use the constants

data/maps/VerdanturfTown_House/scripts.inc

@@ -2,11 +2,11 @@ VerdanturfTown_House_MapScripts:: @ 820335E
 	.byte 0
 
 VerdanturfTown_House_EventScript_20335F:: @ 820335F
-	msgbox VerdanturfTown_House_Text_203371, 2
+	msgbox VerdanturfTown_House_Text_203371, MSGBOX_NPC
 	end
 
 VerdanturfTown_House_EventScript_203368:: @ 8203368
-	msgbox VerdanturfTown_House_Text_2033EE, 2
+	msgbox VerdanturfTown_House_Text_2033EE, MSGBOX_NPC
 	end
 
 VerdanturfTown_House_Text_203371: @ 8203371