Add a test for bad Map polyfill, and work around Rollup bug

[gaearon]

This adds test coverage for these lines:

react/packages/react-reconciler/src/ReactFiber.js

Lines 41 to 51 in 59763bf

	var hasBadMapPolyfill = false;
	try {
	var nonExtensibleObject = Object.preventExtensions({});
	/* eslint-disable no-new */
	new Map([[nonExtensibleObject, null]]);
	new Set([nonExtensibleObject]);
	/* eslint-enable no-new */
	} catch (e) {
	// TODO: Consider warning about bad polyfills
	hasBadMapPolyfill = true;
	}

I only did this for Map because it's a bit hacky, and I figured this would be enough to find regressions.

It fails the bundle tests because apparently Rollup strips the new calls out (which is how we discovered the problem with this check). So I added a workaround for that, and a TODO to report this to Rollup.

[gaearon]

cc @lukastaegert, wondering if it's a known issue?

[acdlite]

Cool test!