[m-rev.] for review: speed up uint32 to string conversion

[Julien Fischer]

On Wed, 27 Oct 2021, Zoltan Somogyi wrote:

> On Wed, 27 Oct 2021 19:53:11 +1100 (AEDT), Julien Fischer <jfischer at opturion.com> wrote:

>> That said, I think the immediate concern should be to replace calls to
>> sprintf() where possible.
>
> Agreed, but it should be done in two phases. First, find the best replacement,
> and then, roll it out to all related conversion functions, not just
> the one for uint32s.

I was intending to do this for all integer types, not just uint32s.
(I started with uints32s because it made comparison with the non-C
grades easier.)

> The best approach *may* differ between e.g.  uintN for different N,
> but probably not by much.

I suspect there may be some difference between the 32-bit and 64-bit
cases and that the other cases can be handled by casting and then
calling the 32-bit or 64-bit case appropriate.

Unless you have any objections I will commit this diff and then add
additional benchmarks and tests for the other integer types.

Julien.