Write structured clone algorithm in terms of ECMAScript

This is based on https://github.com/dslomov/ecmascript-structured-clone with changes to account for
changes in ECMAScript and feedback in #697.

This fixes #697 and also fixes https://www.w3.org/Bugs/Public/show_bug.cgi?id=27031.

This should make it much more explicit how structured cloning actually works and also provides clear
hooks for other standards to use to make their objects cloneable and transferable.