integer-simple by default

[Yitzchak Gale]

Isaac Dupree:
>> We could try to find out how large Integers get, in practice, in
>> existing Haskell code (this may be difficult to find out).

Daniel Fischer wrote:
> Just as a data-point, my code rarely exceeds 128 bits (at least, beyond
> that performance isn't so important anymore).

And Daniel, who is part of the Project Euler team, uses large
integers far more than most people.

As another data point, Python has also re-invented the GMP
wheel, likely for the same licensing reasons. They have
been using a simple implementation of Karatsuba
multiplication for years. I have never heard of anyone
complaining about it. Furthermore, they currently use naive
multiplication and don't even bother with Karatsuba for
less than about 2000 bits on most recent platforms.

Regards,
Yitz