Better error message if cudnnCreate fails with an unfamiliar error code.
Better error message if cudnnCreate fails with an unfamiliar error code.

dpaiton/OpenPV,PetaVision/OpenPV,dpaiton/OpenPV,PetaVision/OpenPV,dpaiton/OpenPV,PetaVision/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,PetaVision/OpenPV,dpaiton/OpenPV,dpaiton/OpenPV,PetaVision/OpenPV,dpaiton/OpenPV