message: Implement DivAssign for BigUint
diff: use std::borrow::Cow;
  use std::default::Default;
  use std::iter::repeat;
  -use std::ops::{Add, BitAnd, BitOr, BitXor, Div, Mul, Neg, Rem, Shl, Shr, Sub, AddAssign, SubAssign, MulAssign};
  +use std::ops::{Add, BitAnd, BitOr, BitXor, Div, Mul, Neg, Rem, Shl, Shr, Sub, AddAssign, SubAssign, MulAssign, DivAssign};
  use std::str::{self, FromStr};
  use std::fmt;
  use std::cmp;
  @@ -635,6 +635,12 @@ impl<'a, 'b> Div<&'b BigUint> for &'a BigUint {
  q
  }
  }
  +impl<'a> DivAssign<&'a BigUint> for BigUint {
  + #[inline]
  + fn div_assign(&mut self, other: &'a BigUint) {
  + *self = &*self / other;
  + }
  +}
  promote_unsigned_scalars!(impl Div for BigUint, div);
  forward_all_scalar_binop_to_val_val!(impl Div<BigDigit> for BigUint, div);
  @@ -649,6 +655,12 @@ impl Div<BigDigit> for BigUint {
  q
  }
  }
  +impl DivAssign<BigDigit> for BigUint {
  + #[inline]
  + fn div_assign(&mut self, other: BigDigit) {
  + *self = &*self / other;
  + }
  +}
  impl Div<BigUint> for BigDigit {
  type Output = BigUint;
  @@ -672,6 +684,12 @@ impl Div<DoubleBigDigit> for BigUint {
  q
  }
  }
  +impl DivAssign<DoubleBigDigit> for BigUint {
  + #[inline]
  + fn div_assign(&mut self, other: DoubleBigDigit) {
  + *self = &*self / other;
  + }
  +}
  impl Div<BigUint> for DoubleBigDigit {
  type Output = BigUint;
  