- RegExp.prototype[Symbol.split] calls ToUint32 (https://github.com/tc39/ecma262/issues/92)
- Species lookup removed from Promise.all and Promise.race (https://github.com/tc39/ecma262/issues/151)
- Generator functions are no longer constructors (https://github.com/tc39/ecma262/pull/171)

Fixes #444

Introduce additional tests to increase parity in coverage between
generator expressions and generator statements.

These tests are derived from the following files within the Google V8
project:

    test/mjsunit/es6/generators-iteration.js
    test/mjsunit/es6/generators-objects.js
    test/mjsunit/es6/generators-runtime.js
    test/mjsunit/es6/generators-states.js