Tightened the arrow function test

This extends the arrow function test to include multiple parameters,
and adds a separate test for lexical "this" (which Chrome 37+ currently
fails).

This does not include the following "pedantic" checks:
* Lexical "arguments"
* No line terminator between parameters and =>
* Absence of "prototype" property, and empty "name" property
Decided to merge the arrow tests back into one

I've changed my mind about having two tests for arrows and lexical this.
Now they're back in the same test, as per the former arrow test pullreq.
(In this case, Chrome 37+ is now failing the test, but the V8 team
[openly admits](http://code.google.com/p/v8/issues/detail?id=2700) that
their arrows aren't production-ready yet.)

Firefox's non-conformance regarding pedantic implementation details is
now noted in footnotes.

I've also converted the test code to a comment string, as per the
others.