This module provides a purely sequential implementation of the
concurrent atomic references provided by the Multicore OCaml
standard library:
https://github.com/ocaml-multicore/ocaml-multicore/blob/parallel_minor_gc/stdlib/atomic.mli
This sequential implementation is provided in the interest of
compatibility: when people will start writing code to run on
Multicore, it would be nice if their use of Atomic was
backward-compatible with older versions of OCaml without having to
import additional compatibility layers. *)