A bit of a pitfall of // is that it doesn't merge recursively which
often leads to unintended deletion in meta sets: If meta is in args it
is also present in the set right of the // operator which means the
right value is used to replace the left value completely. This throws
away anything extra we've set in the meta set in args.
This is fixed by this comment, allowing the descriptions and broken =
true; set in janestreet/old.nix to propagate to the output meta sets.
This contains a collection of Jane Street packages at version 0.9.0.
Packages not already present in ocamlPackages are also made available
without the janeStreet prefix.