test262 bug: trailing comma in export declaration

[dnalborczyk]

[opening seperate issues for tracking purposes]

ExportsList in ExportDeclaration may include a trailing comma

test case: https://github.com/tc39/test262/blob/master/test/language/module-code/instn-iee-trlng-comma.js

export { a , } from './instn-iee-trlng-comma_FIXTURE.js';
export { a as b , } from './instn-iee-trlng-comma_FIXTURE.js';

assert.sameValue(a, 333, 'comma following named export');

ReferenceError: a is not defined
      at file:///test262/test/language/module-code/instn-iee-trlng-comma.js:129:24
      at Generator.next (<anonymous>)

[jdalton]

This isn't about the trailing comma. It's the self circular reference if I had to guess.

Update:

Confirmed this bug is a dup of #544.