mpn_invert_limb

[paul zimmermann]

       Niels,

> > would it be possible to add mpn_invert_limb in the public interface?
> > It would be very useful for GNU MPFR.
> 
> Makes sense to me, it's a useful and well-defined operations, and
> discussed at length in various papers. So should be quite easy to
> document.

great!

Please keep me informed when it happens, so that we can update MPFR accordingly.

Paul