recover some const'ness in Domain class, that was lost when merging MESSAGE...

   if J is not a valid index like -1, just return it

------------------------------------------------------------------------- */

int Domain::closest_image(double *pos, int j)

int Domain::closest_image(const double * const pos, int j)

{

  if (j < 0) return j;

  int *sametag = atom->sametag;

  double **x = atom->x;

  const int * const sametag = atom->sametag;

  const double * const * const x = atom->x;

  int closest = j;

  double delx = pos[0] - x[j][0];

/* ----------------------------------------------------------------------

   find and return Xj image = periodic image of Xj that is closest to Xi

   for triclinic, add/subtract tilt factors in other dims as needed

   called by ServerMD class

   called by ServerMD class and LammpsInterface in lib/atc.

------------------------------------------------------------------------- */

void Domain::closest_image(double *xi, double *xj, double *xjimage)

void Domain::closest_image(const double * const xi, const double * const xj, double * const xjimage)

{

  double dx = xj[0] - xi[0];

  double dy = xj[1] - xi[1];

  void minimum_image(double *);

  void minimum_image_once(double *);

  int closest_image(int, int);

  int closest_image(double *, int);

  void closest_image(double *, double *, double *);

  int closest_image(const double * const, int);

  void closest_image(const double * const, const double * const, double * const);

  void remap(double *, imageint &);

  void remap(double *);

  void remap_near(double *, double *);