De-functorize [Git.Mem] module and constraint it over the type [hash]
De-functorize [Git.Mem] module and constraint it over the type [hash]

Deletion of [Inflate]/[Deflate] modules and use the type [hash] instead the
module [Hash] (see patch about the minimal interface of a Git store). The type
of the store is /de-functorized/ too and it was parameterized by ['hash].

mirage/ocaml-git,mirage/ocaml-git,mirage/ocaml-git