An endianness abstraction

[oscbyspro]

I think I've come up with a nice abstraction for endianness. The idea is that a dynamic enum should be used insofar as it is viable, whereas NBKBigEndian and NBKLittleEndian can be used when performance matters more than binary size (and as a namespace for appropriate methods). As far I can tell, dynamic endianness sensitive collections are viable (#72).

@frozen public struct NBKBigEndian:    NBKEndianness { }
@frozen public struct NBKLittleEndian: NBKEndianness { }
@frozen public enum   NBKAnyEndian:    NBKEndianness { case bigEndian, littleEndian }

---

The latest edition:

enum NBKEndianness: Hashable {
    
    case little
    
    case big

    static var system: Self {
        #if _endian(little)
        return .little
        #elseif _endian(big)
        return .big
        #endif
    }
}

[oscbyspro]

Hm. I think I want the enum, but perhaps the protocol is premature. I'm not sure <Endianess> should be encouraged.

[oscbyspro]

Hm. I'll remove the rawValue and the ! operator. It's unused, and I don't want to overcommit.

[oscbyspro]

An interesting observation: raw values make enum comparisons much faster prior to Swift 5.8. Meh.