Don't allow rename of '.default' property of import

**TypeScript Version:**  nightly (2.2.0-dev.20170124)

**Code**

```ts
/// <reference path='fourslash.ts' />

// @Filename: a.ts
////export default function f() {}

// @Filename: b.ts
////import * as a from "./a";
////a./**/default;

goTo.marker();
verify.renameInfoFailed("!!!");
```

**Expected behavior:**

Rename fails.

**Actual behavior:**

Rename succeeds.