Fix a bug in the Curve25519 module.
Fix a bug in the Curve25519 module.

The parameters were swapped, which was exposed due to the new Curve25519
implementation.

Signed-off-by: Austin Seipp <48c905ac3851f382b914247d97dd93273d5ff555@pobox.com>

thoughtpolice/hs-nacl,thoughtpolice/hs-nacl,thoughtpolice/hs-nacl,thoughtpolice/hs-nacl,thoughtpolice/hs-nacl