Dates, collections and error types match the standard's shape

More of the language's built-in objects now behave exactly as the standard describes. Dates, along with the Map and Set collections and the error, boolean and weak-collection types, present their standard method templates for inspection, and their instances share one set of methods through inheritance the way the standard defines, so a large amount of library and framework code that inspects or borrows these methods now works instead of stopping short. Calling a Map or Set method on a value that is not one now reports a clear error rather than doing nothing, matching every other browser. None of this changes code that was already correct. The JavaScript language aspect moves 91 to 92; the overall platform score stays at 70.