Core: Codestyle clean-up

"pl"->"player"

 Note: codestyle methods needs maintained, Player* player.
still to do properly clean-up chat.cpp.

src/server/game/Entities/Player/Player.h

@@ -2338,7 +2338,7 @@ class Player : public Unit, public GridObject<Player>
 
         bool IsNeverVisible() const;
 
-        bool IsVisibleGloballyFor(Player* pl) const;
+        bool IsVisibleGloballyFor(Player* player) const;
 
         void SendInitialVisiblePackets(Unit* target);
         void UpdateObjectVisibility(bool forced = true);