No message on stack overflow error

When running a test that calls a function that overflows the stack,
only "undefined" is printed instead of the error message, which can
be very confusing.

```
$ nodeunit test-stack-overflow.js

test-stack-overflow.js
✖ test

undefined

FAILURES: 1/1 assertions failed (2ms)
```

test-stack-overflow.js:

``` javascript
function rec() { rec(); };
exports.test = function(test) {
rec();
};
```

I was expecting the error I get when rec() is called directly:

```
test-stack-overflow.js:1
on rec() { rec()
^
RangeError: Maximum call stack size exceeded
```