correct usage of virtual and override for rigid fixes and OpenMP versions

src/OPENMP/fix_rigid_nh_omp.h

@@ -24,10 +24,10 @@ class FixRigidNHOMP : public FixRigidNH {
 
   void initial_integrate(int) override;
   void final_integrate() override;
-  virtual void remap();
+  void remap() override;
 
  protected:
-  virtual void compute_forces_and_torques();
+  void compute_forces_and_torques() override;
 
  private:    // copied from FixRigidOMP
   template <int, int, int> void set_xv_thr();

src/OPENMP/fix_rigid_omp.h

@@ -32,7 +32,7 @@ class FixRigidOMP : public FixRigid {
   void final_integrate() override;
 
  protected:
-  virtual void compute_forces_and_torques();
+  void compute_forces_and_torques() override;
 
  private:
   template <int, int, int> void set_xv_thr();

src/OPENMP/fix_rigid_small_omp.h

@@ -36,7 +36,7 @@ class FixRigidSmallOMP : public FixRigidSmall {
   void final_integrate() override;
 
  protected:
-  virtual void compute_forces_and_torques();
+  void compute_forces_and_torques() override;
 
  private:
   template <int, int, int> void set_xv_thr();

src/RIGID/fix_rigid.h

@@ -145,7 +145,7 @@ class FixRigid : public Fix {
   void setup_bodies_static();
   void setup_bodies_dynamic();
   void apply_langevin_thermostat();
-  void compute_forces_and_torques();
+  virtual void compute_forces_and_torques();
   void enforce2d();
   void readfile(int, double *, double **, double **, double **, imageint *, int *);
 };

src/RIGID/fix_rigid_nh.h

@@ -70,7 +70,7 @@ class FixRigidNH : public FixRigid {
   int tcomputeflag, pcomputeflag;    // 1 = compute was created by fix. 0 = external
 
   void couple();
-  void remap();
+  virtual void remap();
   void nhc_temp_integrate();
   void nhc_press_integrate();
 

src/RIGID/fix_rigid_small.h

@@ -202,7 +202,7 @@ class FixRigidSmall : public Fix {
   void setup_bodies_static();
   void setup_bodies_dynamic();
   void apply_langevin_thermostat();
-  void compute_forces_and_torques();
+  virtual void compute_forces_and_torques();
   void enforce2d();
   void readfile(int, double **, int *);
   void grow_body();