"Fixed" benchmark time is out-of-date in the optimizations section of the testing guide

[huonw]

It currently says

test bench_xor_1000_ints ... bench:       1 ns/iter (+/- 0)

While running the code as written gives

test bench_xor_1000_ints ... bench:       131 ns/iter (+/- 3)

(which is correct.)

[huonw]

(On that note, the code could now be written: let n = test::black_box(1000); instead of having to call black_box separately.)

[steveklabnik]

:(