Work on d_a_mg_fshop (#2006)

include/SSystem/SComponent/c_bg_s_gnd_chk.h

@@ -18,6 +18,7 @@ public:
     void SetNowY(f32 y) { mNowY = y; }
     const cXyz& GetPointP() { return m_pos; }
     u32 GetWallPrecheck() const { return mWallPrecheck; }
+    void OffWall() { mFlags &= ~2; }
 
     /* 0x24 */ cXyz m_pos;
     /* 0x30 */ u32 mFlags;

include/SSystem/SComponent/c_xyz.h

@@ -110,6 +110,7 @@ struct cXyz : Vec {
             z = other.z;
         }
     }
+    void zero() { set(0.0f, 0.0f, 0.0f); }
 
     float getSquareMag() const { return VECSquareMag(this); }
     f32 getSquareDistance(const Vec& other) const { return VECSquareDistance(this, &other); }