Added a test harness 'debug' mode to Simple Test Harness. Accessible via appending

"?sitedebug" to the end of the Test262 URL.

There's a mismatch between the Test262 test harness and IE Test Center's harness
which invalidated 15.4.4.17-5-1.js, 15.4.4.18-5-1.js, and 15.4.4.20-5-1.js on Test262.
Essentially what's going on is Test262 uses the 'window' object as 'this' for the test
case functions whereas IE Test Center uses the test case object housing the test case
function as this.  This causes problems for test cases pertaining to scoping.  I've gone
ahead and adjusted the Test262 tests to expect 'window' to be 'this', and will be updating
IE Test Center's harness to use the 'window' object as well so we don't run into this
problem again.