Add cloud-sync control to PasswordOptions.

[brotskydotcom]

Fixes #229.

This was a slightly more extensive change than I had first thought it would be. For one thing, although the set- and get-password operations had been extended publicly to allow clients to specify PasswordOptions, the delete-password operation had not been, so I added that support.

More importantly, the cloud-sync option for passwords is not binary, it's a tristate with a don't care value. Thus I had to do an enormous amount of testing to understand how the don't-care value affected all three operations. I have reflected the results of my testing in the fairly extensive documentation for set_access_synchronized.

Finally, I had to add the kSecAttrSynchronizationAny tri-state value to the exports of security-framework-sys so that I could use it in set_access_synchronized.

Sadly, the cloud-sync option can only be used from an application that has a provisioning profile with the iCloud capability. Since command-line apps can't have provisioning profiles, I used my rust-on-ios test harness to do this testing, and haven't tried to add any Rust tests to the security framework.

[brotskydotcom]

PR #234 has been merged into this one, so once #234 is merged into the security-framework-sys project then this PR will purely affect only the security-framework project.