This reverts commit a01de4a7.

The global isNaN is not precise at all, and Number.isNaN is an ES6 feature that makes it preferrable to use assert's sameValue for NaN values, as it handles it internally using the comparison.

This commit normalizes the test case format used across test262. It applies the following transformations:

* Convert to YAML for frontmatter
* Remove of trailing whitespace
* Replace /r/n with /n except in chapters 6 and 7.
* Copyright header always uses // comments
* new includes attribute replaces $INCLUDE
* No implicit assumptions about test environment other than $ERROR. Everything else appears in the include array. This includes "runTestCase" which is now included in a substantial number of tests.

source starting NOW, to test/suite.

(between David Fugate and I) canonical test262 test format

assertTrue became assertTruthy. Canonical form of doc-comment attribute value source no longer have a leading colon and trailing semicolon. Any existing such are stripped during conversion.

- external\contributions\: test contributions to Test262 from external entities such as Microsoft and Google.
                           This directory consists of the external tests without any modifications
- test\harness\:  test harness used to run Test262 tests.  Presently web-based
- test\suite\:    suite of vendor-neutral ECMAScript test cases conforming to the ES5 spec
- tools\:         among other things this includes a set of tools used to convert various external test
                  contributions to a format the Test262 test harness can consume
- website\:       an archived copy of the http://test262.ecmascript.org website