JSON conversion matches the standard, including circular data

JavaScript's built-in JSON conversion brought closer to the standard. Turning data that refers back to itself into JSON now reports a clear error the way every browser does, instead of running away until the page freezes. Choosing exactly which fields to include now follows the order you list them in and drops duplicates, as the standard describes. And controlling the indentation of the output with a wrapped number or piece of text now works, including any custom conversion that value defines. Code that was already correct is unchanged. The JavaScript language aspect moves 94 to 95; the overall platform score stays at 70.