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/PetalburgCity_House2/scripts.inc

@@ -2,11 +2,11 @@ PetalburgCity_House2_MapScripts:: @ 82078F2
 	.byte 0
 
 PetalburgCity_House2_EventScript_2078F3:: @ 82078F3
-	msgbox PetalburgCity_House2_Text_207905, 2
+	msgbox PetalburgCity_House2_Text_207905, MSGBOX_NPC
 	end
 
 PetalburgCity_House2_EventScript_2078FC:: @ 82078FC
-	msgbox PetalburgCity_House2_Text_207969, 2
+	msgbox PetalburgCity_House2_Text_207969, MSGBOX_NPC
 	end
 
 PetalburgCity_House2_Text_207905: @ 8207905