ad part [`Relaxed`].

# Examples

```
use portable_atomic::{AtomicI64, Ordering};

let foo = AtomicI64::new(23);
assert_eq!(foo.fetch_max(42, Ordering::SeqCst), 23);
assert_eq!(foo.load(Ordering::SeqCst), 42);
```

If you want to obtain the maximum value in one step, you can use the following:

```
use portable_atomic::{AtomicI64, Ordering};

let foo = AtomicI64::new(23);
let bar = 42;
let max_foo = foo.fetch_max(bar, Ordering::SeqCst).max(bar);
assert!(max_foo == 42);
```