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/SafariZone_North/scripts.inc

@@ -2,10 +2,10 @@ SafariZone_North_MapScripts:: @ 823D253
 	.byte 0
 
 SafariZone_North_EventScript_23D254:: @ 823D254
-	msgbox SafariZone_North_Text_2A5489, 2
+	msgbox SafariZone_North_Text_2A5489, MSGBOX_NPC
 	end
 
 SafariZone_North_EventScript_23D25D:: @ 823D25D
-	msgbox SafariZone_North_Text_2A54F0, 2
+	msgbox SafariZone_North_Text_2A54F0, MSGBOX_NPC
 	end