use Object.defineProperty to provide a Symbol.create impl, instead of an assignment.  fixes #161
ES6: Updated the default parameters test

Added the following checks:
* Explicitly passing undefined defers to the default
* Later defaults may reference values of earlier parameters

This doesn't add the following "pedantic" checks:
* Earlier defaults may not reference values of later parameters
* Defaults may use the arguments object.
* Defaults affect the function length property.
Fixed an ES5 strict test that crashes in Chrome

The test `(function f() { f = 123; })()` actually throws a SyntaxError
on evaluation, not a TypeError on execution, in the current Chrome. I'm
really not sure which is fully correct for either the ES5 or ES6 specs.
Nevertheless, I've changed that line to be eval()ed so that the entire
script doesn't crash.

Also, the link to the strict mode page is fixed.
ES6: Added super test

This checks that:
* super() in the constructor binds to the superclass's constructor
* super.X() in the constructor binds to the superclass's X method
* super() in the X method binds to the superclass's X method
* super is bound statically, and remains bound even when a method is
extracted
Fix unscopables test
Fix invalid Symbol.iterator test

The test was using Function() which implies global scope. Since
the test tries to access the local variable b there was a
ReferenceError.

Changed the test to use eval instead.
Merge pull request #202 from arv/iterator

Fix invalid Symbol.iterator test
Merge pull request #201 from arv/unscopables

Fix unscopables test
ES6: Added Typed Arrays test

This tests every available heterogenous array view, by setting beyond
the given type's maximum, and checking if it overflowed in a manner
consistent with the type.

Usage data was largely taken from CanIUse.

NOTE: this does NOT check DataView - a separate test will have to be
made for it, which is good as it actually has slightly different support
values (for instance, only Firefox 15+ supports it).
Updated the generator test to include yield*

The yield* keyword, as you know, successively yields values from the
given iterable until it's exhausted.

This also removes the "application/javascript;version=1.8" version of
the test, which actually didn't influence anything in Firefox w/r/t
this feature.

This test change doesn't alter any of the support results.
WebKit now supports Math.sign and multi-d11g

(d11g = destructuring)
Merge pull request #211 from webbedspace/webkit172711

WebKit now supports Math.sign and multi-destructuring
Corrected #201 and #202

I just noticed that pulls #201 and #202 actually edited the HTML file
instead of the data-es6.js file. This fixes that.
Merge pull request #212 from webbedspace/gh-pages

Corrected #201 and #202
Added note to WeakMap and WeakSet results

WeakMap and WeakSet constructor arguments, such as new WeakSet([obj1,
obj2]), are not supported in most browser platforms.
Added a further note to Map and Set results

Additionally, it seems only Firefox supports arguments to the Map() and
Set() constructors.
Merge pull request #198 from webbedspace/super

ES6: Added super test
Merge pull request #208 from webbedspace/weakmapnote

Added note to WeakMap and WeakSet results
FF34 now supports shorthand methods
Fix Array.prototype[Symbol.unscopables] test

The unscobables of the Array.prototype is no longer an Array.