Handle computed property names in overloads

**TypeScript Version:**  nightly (2.5.0-dev.20170719)

**Code**

```ts
class C {
    ["foo"](): void
    ["bar"](): void;
    ["foo"]() {
        return 0;
    }
}
```

**Expected behavior:**

An error: the overload is being called `"bar"` where it should be `"foo"`.

**Actual behavior:**

No error.