Re-exporting namespace declarations in ES6 ambient declaration

Right now many declaration files take this form:

``` typescript
declare namespace MyLib {

}

declare module 'myLib' {
export = MyLib;
}
```

However, there doesn't seem to be an equivalent for ES6 modules:

``` typescript
declare module 'myLib' {
export default MyLib; // this works for exporting the default, but other exported items in MyLib are not considered to be named exports of the ES6 module
export * from MyLib; // this is essentially what I'm trying to accomplish
}
```

The issue names no files or tests. Start with TypeScript's handling of ambient namespace declarations and ES6 module exports, then determine the intended re-export semantics for MyLib. Done means the namespace members are recognized as named exports of the declared ES6 module, with the behavior verified by suitable compiler tests.

Written by the indexing model from the issue text.