[ANN] containers 2.0

I’m happy to announce that Containers 2.0 is released and should land on opam shortly.

There were some improvements since the last announce. The new changelog is there. However, the core of the changes is that dangerous polymorphic operators are hidden after open Containers, and are not relied upon anymore.

There is a migration guide for updating your code to 2.0. In short, open Pervasives following open Containers might ease the transition; printing functions are all named pp; and some optional arguments are now mandatory.