OpenMP firstprivate clashes with NVIDIA compiler

[mknaranja]

When using CUDA with NVC++ on branch `15-consider-cuda-implementation-of-essential-code-parts, we get a lot of

NVC++-S-0155-A possibly throwing copy constructor for a task firstprivate variable is not supported  (/gpfsscratch/rech/emp/utd66dd/cuda/GMGPolar/src/smoother.cpp: 2291)
NVC++-S-0155-A possibly throwing copy constructor for a task firstprivate variable is not supported  (/gpfsscratch/rech/emp/utd66dd/cuda/GMGPolar/src/smoother.cpp: 2291)
NVC++-S-0155-A possibly throwing copy constructor for a task firstprivate variable is not supported  (/gpfsscratch/rech/emp/utd66dd/cuda/GMGPolar/src/smoother.cpp: 2291)
NVC++-S-0155-A possibly throwing copy constructor for a task firstprivate variable is not supported  (/gpfsscratch/rech/emp/utd66dd/cuda/GMGPolar/src/smoother.cpp: 2291)
NVC++-S-0155-A possibly throwing copy constructor for a task firstprivate variable is not supported  (/gpfsscratch/rech/emp/utd66dd/cuda/GMGPolar/src/smoother.cpp: 2291)
NVC++-S-0155-A possibly throwing copy constructor for a task firstprivate variable is not supported  (/gpfsscratch/rech/emp/utd66dd/cuda/GMGPolar/src/smoother.cpp: 2291)

messages caused by lines like https://github.com/mknaranja/GMGPolar/blob/15-consider-cuda-implementation-of-essential-code-parts/src/smoother.cpp#L2291