Add `byteorder` type methods to extract native value without performing byteorder swap

These should probably be named `to_bits` to be consistent with the methods of the same name on `f32` and `f64`. The alternative would be something like `get_native`, but I worry that that's too close to `get`, and it'd be too much of a footgun - it'd be easy to reach for it without realizing that it doesn't perform an endianness swap.