RFR 8044520: Nashorn cannot execute node.js's express module

[A. Sundararajan]

Please review.

Webrev: http://cr.openjdk.java.net/~sundar/8044520/
Bug: https://bugs.openjdk.java.net/browse/JDK-8044520

Relevant sections of ES6 draft spec. are these:

* [[SetPrototypeOf]] builtin
https://people.mozilla.org/~jorendorff/es6-draft.html#sec-ordinary-object-internal-methods-and-internal-slots-setprototypeof-v 
<https://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-ordinary-object-internal-methods-and-internal-slots-setprototypeof-v>

* Object.prototype.__proto__ special property:
https://people.mozilla.org/~jorendorff/es6-draft.html#sec-additional-properties-of-the-object.prototype-object 
<https://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-additional-properties-of-the-object.prototype-object>

* Object.setPrototypeOf function:
https://people.mozilla.org/~jorendorff/es6-draft.html#sec-object.setprototypeof 
<https://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-object.setprototypeof>

* __proto__ property name in object initializers:
https://people.mozilla.org/~jorendorff/es6-draft.html#sec-__proto__-property-names-in-object-initializers 
<https://people.mozilla.org/%7Ejorendorff/es6-draft.html#sec-__proto__-property-names-in-object-initializers>

PS. Hopefully, I won't have to do any more __proto__, setPrototypeOf 
fixes ;-)

Thanks,
-Sundar