Add support for Math.IEEEremainder

[dasa]

Is your feature request related to a problem? Please describe.

Math.IEEEremainder isn't implemented and is commented as such at: https://github.com/google/j2cl/blob/master/jre/java/java/lang/Math.java#L34

Describe the solution you'd like

Add support for Math.IEEEremainder

Describe alternatives you've considered

I attempted an implementation based on this doc:

	static private double IEEEremainder(double dividend, double divisor) {
		return dividend - (divisor * Math.round(dividend / divisor));
	}

Additional context

The link above shows expected output, and there are tests for the Kotlin implementation.

[gkdn]

Thanks for the detailed report. Would you like to send a PR?

[aschleck]

Might as well note: my understanding is the implementation above is incorrect. Math.IEEEremainder rounds towards even but Math.round does not.

I never bothered cleaning up this janky implementation but I think it is correct:

IEEEremainder = function(f1, f2) {
  // f1 - f2 * round_towards_even(f1 / f2)
  const div = f1 / f2;
  let rounded;
  const remainder = div % 1;
  if (remainder === 0.5 || remainder === -0.5) {
    const fn = div < 0 ? Math.ceil : Math.floor;
    rounded = fn(div) + fn(div % 2);
  } else {
    rounded = Math.round(div);
  }
  return f1 - (f2 * rounded)
}

Hesitant to PR it since it looks so hacky