Merge pull request #344 from bocoup/SetIteratorPrototype

test/built-ins/SetIteratorPrototype/Symbol.toStringTag.js

...type/next/does-not-have-mapiterator-internal-slots-set.js

...rototype/next/does-not-have-mapiterator-internal-slots.js

.../built-ins/SetIteratorPrototype/next/iteration-mutable.js

test/built-ins/SetIteratorPrototype/next/iteration.js

test/built-ins/SetIteratorPrototype/next/no-set-data.js

...etIteratorPrototype/next/this-not-object-throw-entries.js

...s/SetIteratorPrototype/next/this-not-object-throw-keys.js

...rototype/next/this-not-object-throw-prototype-iterator.js

...SetIteratorPrototype/next/this-not-object-throw-values.js