message: fix endianness of to/from_doublebigdigit calls
diff: @@ -429,7 +429,7 @@ impl Add<DoubleBigDigit> for BigUint {
  self.data.push(0);
  }
  - let (lo, hi) = big_digit::from_doublebigdigit(other);
  + let (hi, lo) = big_digit::from_doublebigdigit(other);
  let carry = __add2(&mut self.data, &[lo, hi]);
  if carry != 0 {
  self.data.push(carry);
  @@ -497,7 +497,7 @@ impl Sub<DoubleBigDigit> for BigUint {
  #[inline]
  fn sub(mut self, other: DoubleBigDigit) -> BigUint {
  - let (lo, hi) = big_digit::from_doublebigdigit(other);
  + let (hi, lo) = big_digit::from_doublebigdigit(other);
  sub2(&mut self.data[..], &[lo, hi]);
  self.normalize()
  }
  @@ -512,7 +512,7 @@ impl Sub<BigUint> for DoubleBigDigit {
  other.data.push(0);
  }
  - let (lo, hi) = big_digit::from_doublebigdigit(self);
  + let (hi, lo) = big_digit::from_doublebigdigit(self);
  sub2rev(&[lo, hi], &mut other.data[..]);
  other.normalize()
  }
  @@ -561,7 +561,7 @@ impl Mul<DoubleBigDigit> for BigUint {
  } else if other <= BigDigit::max_value() as DoubleBigDigit {
  self * other as BigDigit
  } else {
  - let (lo, hi) = big_digit::from_doublebigdigit(other);
  + let (hi, lo) = big_digit::from_doublebigdigit(other);
  mul3(&self.data[..], &[lo, hi])
  }
  }
  @@ -624,7 +624,7 @@ impl Div<BigUint> for DoubleBigDigit {
  match other.data.len() {
  0 => panic!(),
  1 => From::from(self / other.data[0] as u64),
  - 2 => From::from(self / big_digit::to_doublebigdigit(other.data[0], other.data[1])),
  + 2 => From::from(self / big_digit::to_doublebigdigit(other.data[1], other.data[0])),
  _ => Zero::zero(),
  }
  }
  