where they both use the same limb size. I've tweaked his patch slightly, so
blame me if it breaks.

Submitted by: Paul Sheer
Reviewed by: Geoff Thorpe

already built and tested.

key operations using the GMP library. The default is not to build (or use)
this code unless OPENSSL_USE_GMP is defined (because it will impose header
and linker dependencies that might need specifying too).