rem: find_line (unsigned int linenum)
add: find_line (uintmax_t linenum)
context: find_line (unsigned int linenum){  struct buffer_record *b;  if (head == NULL && !load_buffer ())    return NULL;  if (linenum < head->start_line)    return NULL;  for (b = head;;)    {      if (linenum < b->start_line + b->num_lines)	{	  /* The line is in this buffer. */	  struct line *l;	  unsigned int offset;	/* How far into the buffer the line is. */	  l = b->line_start;	  offset = linenum - b->start_line;	  /* Find the control record. */	  while (offset >= CTRL_SIZE)	    {	      l = l->next;	      offset -= CTRL_SIZE;	    }	  return &l->starts[offset];	}      if (b->next == NULL && !load_buffer ())	return NULL;      b = b->next;		/* Try the next data block. */    }}