added back cuda.h includes to fix missing CUDA_VERSION

nvcc doesn't define its version identity macro, CUDA_VERSION, by default,
but this needs to be pulled in through cuda.h. Quite weird and
non-standard behavior, but as swithing to legacy kernels and certain
kernel optimizations are broken now, to fix these we need to include
cuda.h.

Change-Id: I4836335e97a287e18e595c160819db2e46a8d798
Merge "added back cuda.h includes to fix missing CUDA_VERSION" into release-4-6