[m-rev.] for post-commit review: add casts to and from uint32 and uint16

[Julien Fischer]

On Fri, 7 Jan 2022, Zoltan Somogyi wrote:

> On Mon, 3 Jan 2022 18:18:57 +1100 (AEDT), Julien Fischer <jfischer at opturion.com> wrote:
>> For post-commit review by anyone.
>
> The diff is fine as far as it goes, by I don't think
> we should add such operations piecemeal, because this
> can introduce gratuitous differences between {int,uint}*.m.
> For example, after this diff, uint32.m contains casts to and from
> uint8s and uint16s, but int32.m contains casts to and from
> neither int8s or int16s.

I'll add the signed versions. I needed the unsigned casts for some of
the work I have been doing with unsigned integer to string conversion;
once I move onto the signed conversions we will need the signed casts as
well.

Julien.