Add way of getting correct ctypes integer type for bigint, tagint, and imageint

import re

import sys

def get_ctypes_int(size):

  if size == 4:

    return c_int32

  elif size == 8:

    return c_int64

  return c_int

class MPIAbortException(Exception):

  def __init__(self, message):

    self.message = message

    # optional numpy support (lazy loading)

    self._numpy = None

    # set default types

    self.c_bigint = get_ctypes_int(self.extract_setting("bigint"))

    self.c_tagint = get_ctypes_int(self.extract_setting("tagint"))

    self.c_imageint = get_ctypes_int(self.extract_setting("imageint"))

  def __del__(self):

    if self.lmp and self.opened:

      self.lib.lammps_close(self.lmp)

    ptr = self.lib.lammps_extract_atom(self.lmp,name)

    return ptr

  # extract lammps type byte sizes

  def extract_setting(self, name):

    if name: name = name.encode()

    self.lib.lammps_extract_atom.restype = c_int

    return int(self.lib.lammps_extract_setting(self.lmp,name))

  @property

  def numpy(self):

    if not self._numpy: