109.32.00

- Normalized `Command`'s help messages.

  Made anonymous argument names uppercase and subcommand names lowercase.

- In `Iobuf`, added duals to `flip` and `snapshot` to work on the high end of the window.

  `flip` has been renamed to `flip_lo`.  The dual of `flip_lo` is the
  newly added `flip_hi`, and shifts the window forward to continue
  reading, rather than back to switch from writing to reading, as
  `flip_lo` does.

  `flip_hi`, in practice, needs snapshots of the upper bound of the
  window, we split `Snapshot` into `Lo_bound` and `Hi_bound` and
  introduced bounded versions of `flip_lo`, `compact`, and `flip_hi` to
  support buffers which are only partially filled, but have
  substructure, like packet buffers.

  Here's the new API.

  ```ocaml
  module type Bound = sig
    type ('d, 'w) iobuf

    (** Expose =t = private int= only if a =t= is stored in a mutable data structure
       somewhere and leads to a measurable =caml_modify= performance problem. *)
    type t with sexp_of

    val window : (_, _) iobuf -> t
    val limit  : (_, _) iobuf -> t
    val restore : t -> (_, seek) iobuf -> unit
  end
  module Lo_bound : Bound
  module Hi_bound : Bound
  val flip_lo         : (_, seek) t -> unit
  val bounded_flip_lo : (_, seek) t -> Lo_bound.t -> unit
  val flip_hi         : (_, seek) t -> unit
  val bounded_flip_hi : (_, seek) t -> Hi_bound.t -> unit
  ```