use the GMP library for Math::BigInt routines
Provides support for big integer calculations via the GMP c-library.

Math::BigInt::GMP now no longer uses Math::GMP, but provides its own XS
layer to access the GMP c-library. This cuts out another (perl sub routine)
layer and also reduces the memory footprint by not loading Math::GMP and
Carp at all.

Maintainer: The OpenBSD ports mailing-list <ports@openbsd.org>
