Add two new multiply benchmarks testing large factors of unequal sizes

test multiply_0           ... bench:          42 ns/iter (+/- 0)
test multiply_1           ... bench:       4,271 ns/iter (+/- 68)
test multiply_2           ... bench:     289,339 ns/iter (+/- 10,532)
test multiply_3           ... bench:     663,387 ns/iter (+/- 17,381)
test multiply_4           ... bench:       7,474 ns/iter (+/- 384)
test multiply_5           ... bench:      16,376 ns/iter (+/- 254)

Author: joelonsql

benches/bigint.rs

@@ -87,6 +87,16 @@ fn multiply_3(b: &mut Bencher) {
     multiply_bench(b, 1 << 16, 1 << 17);
 }
 
+#[bench]
+fn multiply_4(b: &mut Bencher) {
+    multiply_bench(b, 1 << 12, 1 << 13);
+}
+
+#[bench]
+fn multiply_5(b: &mut Bencher) {
+    multiply_bench(b, 1 << 12, 1 << 14);
+}
+
 #[bench]
 fn divide_0(b: &mut Bencher) {
     divide_bench(b, 1 << 8, 1 << 6);