obj_movebox mostly done (#2181)

include/d/bg/d_bg_s.h

@@ -108,7 +108,7 @@ public:
     fopAc_ac_c* PushPullCallBack(cBgS_PolyInfo const&, fopAc_ac_c*, s16, dBgW_Base::PushPullLabel);
 
     bool WaterChk(dBgS_SplGrpChk* chk) { return SplGrpChk(chk); }
-    u32 GetMtrlSndId(cBgS_PolyInfo* param_0) { return dKy_pol_sound_get(param_0); }
+    u32 GetMtrlSndId(const cBgS_PolyInfo& param_0) { return dKy_pol_sound_get(&param_0); }
 };  // Size: 0x1404
 
 bool dBgS_CheckBGroundPoly(cBgS_PolyInfo const&);

include/d/bg/d_bg_s_movebg_actor.h

@@ -20,6 +20,7 @@ public:
     /* 80078950 */ int MoveBGExecute();
 
     int MoveBGDraw() { return Draw(); }
+    int MoveBGIsDelete() { return IsDelete(); }
 
     /* 80078688 */ virtual int CreateHeap();
     /* 80078690 */ virtual int Create();