Add support for new-style SecAccessControlCreateFlags constants

[LinusU]

Fixes #172

[CLAassistant]

All committers have signed the CLA.

[dfed]

🤔. Looks like Xcode 9 (our minimum-supported Xcode version) doesn't like the new fields. Looks like there is no good way to handle renames of option set values over multiple Xcode version.

You might want to consider (and I know this sucks) using SecAccessControlCreateFlags.init(rawValue:) to avoid the warning. Consider instead of

if #available(macOS 10.12.1, *) {
    return .touchIDAny
} else {
    ErrorHandler.assertionFailure(".biometricAny requires macOS 10.12.1.")
    return .userPresence
}

We could write

if #available(macOS 10.12.1, *) {
    return .init(rawValue: 2) // .biometryAny with Xcode 9 compatibility.
} else {
    ErrorHandler.assertionFailure(".biometricAny requires macOS 10.12.1.")
    return .userPresence
}

biometryCurrentSet's raw value is 8, so you could do the same thing there.

Thoughts? I want to provide a warning-free Valet for you, but with Swift's limitations (and my not wanting to do a major version bump to drop Xcode 9), I'm not seeing better options.

[dfed]

@LinusU let me know what you think of the above. I'd love to see a fix for our warnings land on master with you as the author.

That said, I don't want to wait forever on this – warnings are annoying, and I don't want to burden our consumers with them for longer than I must. If I don't hear from you by Monday June 3rd, I'll likely put up a PR to remove these warnings.

[LinusU]

So sorry for the delay on this!

Took your approach and also rebased on master, thanks! ☺️

[dfed]

LGTM! Thank you for making the fix backwards-compatible. Excited to release this and get back to zero warnings 🚀