Renamed BATTLELINKMSGTYPE_ to BATTLELINKCOMMTYPE_

I want to avoid the word "message" since PRET has already chosen "battle message" as the term for predefined strings usable in the battle scripts and UI.

I was considering the term "battle link packet" instead, but the library for wireless communications already uses the word "packet" even though GBATEK does not. I'm going with "battle link communication type" instead. For this particular context, I don't think we need a compound noun ("X type"); the singular noun "type" is fine enough.

include/battle_controllers.h

@@ -108,9 +108,9 @@ enum {
 // Special arguments for Battle Controller functions.
 
 enum {
-   BATTLELINKMSGTYPE_ENGINE_TO_CONTROLLER, // gBattleBufferA
-   BATTLELINKMSGTYPE_CONTROLLER_TO_ENGINE, // gBattleBufferB
-   BATTLELINKMSGTYPE_CONTROLLER_BECOMING_IDLE
+   BATTLELINKCOMMTYPE_ENGINE_TO_CONTROLLER, // gBattleBufferA
+   BATTLELINKCOMMTYPE_CONTROLLER_TO_ENGINE, // gBattleBufferB
+   BATTLELINKCOMMTYPE_CONTROLLER_BECOMING_IDLE
 };
 
 enum {