fix `equal`

[agarwal]

It still assumes that two paths are equal if their normalizations are equal, but we decided that the explicit structure of a path matters. Thus, equal should now be OCaml's polymorphic equal.

[agarwal]

I'm wrong. We decided that we should not resolve links. Normalization just eliminates Dots and Dotdots, which should be disregarded for equality checking. In the rare case that someone even cared about these, you can use OCaml's polymorphic equality. So the current implementation is already what we want.