fixed include, fixed numdiff forces getting called before initialization

src/fix_numdiff.h

@@ -48,12 +48,12 @@ private:
 
   double **numdiff_forces;          // finite diff forces
   double **temp_f;                  // original forces
-  double **temp_x;                  // original coords
 
   double update_energy(int vflag);
   void force_clear(double **forces);
   void create_groupmap();
   void displace_atom(int local_idx, int direction, int magnitude);
+  void reset_atom_position(int local_idx, int direction, double position);
   void calculate_forces(int vflag);
 };