Use Object.is instead of === to implement phys_equal #1372
Description
There are a few places where the behavior of phys_equal differ between native OCaml and Jsoo:
| a | b | native | jsoo |
|---|---|---|---|
| NaN | NaN | true | false |
| 0.0 | -0.0 | false | true |
The (relatively) new Object.is function implements those comparisons "correctly":
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/is