[PATCH v2 (Draft)] emacs: split async json parser into utility function

[David Bremner]

Mark Walters <markwalters1009 at gmail.com> writes:

> Split out the json parser into a utility function.
> ---
>
> Most of this patch is code movement: but I don't see how to arrange the
> patch to show that.
>

"git gui blame notmuch.el" gives some clues, although it isn't perfect.
Maybe you could explain in the commit message what is _not_ code
movement?

> +(defvar notmuch-json-parser nil
> +  "Incremental JSON parser.")

This docstring needs expanding. I suppose that this is for internal use,
but it isn't clear from the docstring.