Install Error.prepareStackTrace before any errors are thrown.

A recent change to v8 made it so that Error.prepareStackTrace is called
when an error is thrown, not when the stack property is retrieved:

    https://code.google.com/p/v8/issues/detail?id=2559
Fixed failing integration test, caused by 24f6e65a7844722685a24fe03b7bea6a5bdfe568.
Fixed a whitespace problem.
Brought a comment up to date.