Allow imported module members to be named default

[GeoffreyBooth]

Closes #4387.

Apparently code like this is not only allowed in ES2015, it’s common:

import { default } from 'lib';

Although import default from 'lib'; is not allowed in ES.

This PR allows destructured import (and export-import) of module members named default.

[lydell]

I never stop learning new stuff about import/export. Good work!

[GeoffreyBooth]

Too bad we didn’t slip this in before 1.12.0. Well, I guess it won’t be long before 1.12.1 . . .

[lydell]

We could do 1.12.1 as soon as possible, if you feel like it.

[GeoffreyBooth]

Let’s see what else people find in the next few days?

There was a workaround for #4387, it occurs to me now. One could always have done:

import * as lib from 'lib'
def = lib.default

So there shouldn’t be too much urgency in getting this fix released.