rem: getusershell ()
add: getusershell (void)
context: getusershell (){  if (default_index > 0)    {      if (default_shells[default_index])	/* Not at the end of the list yet.  */	return xstrdup (default_shells[default_index++]);      return NULL;    }  if (shellstream == NULL)    {      shellstream = fopen (SHELLS_FILE, "r");      if (shellstream == NULL)	{	  /* No shells file.  Use the default list.  */	  default_index = 1;	  return xstrdup (default_shells[0]);	}    }  while (readname (&line, &line_size, shellstream))    {      if (*line != '#')	return line;    }  return NULL;			/* End of file. */}