integer-simple by default

[Florian Weimer]

* Greg Fitzgerald:

>> You can dynamically link libgmp on windows. That might be easier:
>
> Do you know if the dynamic link escape hatch has ever held up in
> court?

GMP is LGPL, so if you use an official build or a private build from
unmodified sources, all you need to do is to ship the sources along
with your product.

(In theory.  Ask a lawyer to be sure.)