fails:BigDecimal#mod_part_of_divmod returns the dividend if the divisor is Infinity
fails:BigDecimal#mod_part_of_divmod raises ZeroDivisionError if other is zero
fails:BigDecimal#divmod raises ZeroDivisionError if the divisor is zero
fails:BigDecimal#divmod returns an array of Infinity and NaN if the dividend is Infinity
fails:BigDecimal#divmod returns an array of zero and the dividend if the divisor is Infinity
