Incorrect emit for ES6 export default class with static initializers

Given the following TypeScript:

``` ts
export default class {
  static x = 1;
}
```

We emit the following JavaScript:

``` ts
export default class {
}
default_1.x = 1; // TypeError: Cannot set property 'x' of undefined
```

Where we should emit the following instead:

``` ts
export default class default_1 { // generated
}
default_1.x = 1;
```
