Tests for changes introduced in ES2015 (Annex E)

- String case functions iterate over code points
- Has called before Get in Array.p.reverse
- Add test for web-compat Array.p.splice behaviour; Plus missing test for no arguments case
- ToObject no longer applied to this-value in Array.p.toLocaleString
- ToObject no longer applied to this-value in Object.p.toLocaleString
- Add tests for Object.p.propertyIsEnumerable and symbol property keys
- Add tests for Object.p.hasOwnProperty and symbol property keys
- Test property descriptor attributes of message property
- Tests for RegExp constructor checks
- Date constructor when called with date object
- TimeClip never returns negative zero