Incorrect emits with function return type declarations

**TypeScript Version:**  master

**Code**

`$ node built/local/tsc.js -t es5 -m amd --moduleResolution node --lib es6 index.ts`

``` ts
function f(): undefined {
  return;
}
```

**Expected behavior:**

``` js
function f() {
    return;
}
```

**Actual behavior:** 

``` js
function f():  {
    return;
}
```
