Support ES `export * as ns from` form

[mhegazy]

The ES7 proposal is available at: https://github.com/leebyron/ecmascript-more-export-from

The additions include:

reexporting default:

// proposed:
export v from "mod";

// symmetric to:
import v from "mod";
export {v};

reexporting as sub-module:

// proposed:
export * as ns from "mod";

// symmetric to:
import * as ns from "mod";
export {ns};

also allowing combining

// proposed
export v, {x, y as w} from "mod"
// symmetric to
import v, {x, y as w} from "mod"
As well as

// proposed
export v, * as ns from "mod"
// symmetric to
import v, * as ns from "mod"

[vilicvane]

👍