Handle `@extends` jsdoc tag

TypeScript Version: nightly (2.5.0-dev.20170707)

Code

C.d.ts

export default class C<T> {
    t: T;
}

D.js

import C from "./C";

/** @extends {C<number>} */
class D extends C {}

new D().t;

Expected behavior:

t is of type number.

Actual behavior:

t is of type any.

See also #17073.