[m-rev.] for review: add casts to and from uint{16, 32, 64} and uint8

[Julien Fischer]

On Sun, 7 Nov 2021, Julien Fischer wrote:

> For review by anyone.
>
> ---------------------
>
> Add casts to and from uint{16,32,64} and uint8.
>
> While these casts can be implemented by casting via uint, the resulting code 
> is
> less readable than code that uses direct casts.
>
> library/uint16.m:
> library/uint32.m:
> library/uint64.m:
>     Add cast_from_uint8/1 and cast_to_uint8/1 to these modules.
>
> NEWS:
>     Announce the above additions.
>
> tests/hard_coded/Mmakefile:
> tests/hard_coded/uint{16,32,64}_uint_casts.{m,exp}:
>     Add tests for the new casts.

In the absence of any review comments, I intend to commit this one
this evening.

Julien.