message: Add a bench for bigint multiply
  This bench allows to see the increase of time
  if we double the size of one of the operands.
diff: @@ -78,6 +78,11 @@ fn multiply_2(b: &mut Bencher) {
  multiply_bench(b, 1 << 16, 1 << 16);
  }
  +#[bench]
  +fn multiply_3(b: &mut Bencher) {
  + multiply_bench(b, 1 << 16, 1 << 17);
  +}
  +
  #[bench]
  fn divide_0(b: &mut Bencher) {
  divide_bench(b, 1 << 8, 1 << 6);
  