Introduce structuredClone() to global

[botic]

This would implement a standard-based deep clone function. This would make a good addition in RingoJS 3.1 and looks like an Ringo-side implementation to mee. Otherwise we could implement it directly in Rhino's global, but it will not be part of ECMAScript, so I see not a huge chance for it. See

• https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Structured_clone_algorithm
• https://simonplend.com/deep-clone-values-with-structuredclone/