wip/creal 0.7nb1 NetBSD

Creal is an exact real arithmetic library (constructive reals) for ocaml

Creal actually contains two different implementations:

\* Creal: from the PhD thesis of Valerie Menissier-Morain (.ps)
\* Cr: port of Hans Boehm's Java CR library

The two interfaces are almost identical, so that it is easy to switch from one to the other, unless you are using the approx function directly: in Creal, it gives an approximation up to 1/4^n, and in Cr up to 2^n

Both implementations are based on mlgmp by David Monniaux (included in this pkg)