Fix reordering components that return Fragments

[luwes]

This should ideally work, I couldn't find a solution right away.
This PR fixed the same bug in Preact: preactjs/preact#1515

little-vdom/test.jsx

Lines 376 to 407 in 3b1b149

	it.skip('should handle reordering components that return Fragments #1325', () => {
	const X = (props) => {
	return props.children;
	}
	const App = (props) => {
	if (props.i === 0) {
	return (
	<div>
	<X key={1}>1</X>
	<X key={2}>2</X>
	</div>
	);
	}
	return (
	<div>
	<X key={2}>2</X>
	<X key={1}>1</X>
	</div>
	);
	}
	render(<App i={0} />, scratch);
	expect(scratch.textContent).to.equal('12');
	clearLog();
	console.log('----------------------------------');
	render(<App i={1} />, scratch);
	console.log(getLog());
	expect(scratch.textContent).to.equal('21');
	});