Make a proxy NVCC_compiler that does not create a second context on the card as a side effect.

Cuda docs suggest that more than one context on a card may slow down operations, so this might give us a slight win.
Remember the device init_dev() was called with.
Fix the device='cuda' case.
Merge pull request #1874 from abergeron/gpuarray_nvcc

Make a proxy NVCC_compiler that does not create a second context on the card as a side effect.