rem: df_readable (int negative, uintmax_t n, char *buf,
add: df_readable (bool negative, uintmax_t n, char *buf,
context: df_readable (int negative, uintmax_t n, char *buf,	     uintmax_t input_units, uintmax_t output_units){  if (n == -1)    return "-";  else    {      char *p = human_readable (negative ? -n : n, buf + negative,				human_output_opts, input_units, output_units);      if (negative)	*--p = '-';      return p;    }}