Add CUDA nvcc >=7.0 support
With CUDA 7.x, there is a few % performance benefit to using sm_52
arch as target instead of JIT-ed compute_50, mostly relevant with
the newly released v7.5 (as v7.0 has other regressions which make it
slower).
This change adds a single new target architecture (5.2) and changes
the virtual architecture included in the binary from 5.0 to 5.2 with
new enough nvcc to make 5.1.x versions future-proof when new hardware is
released.
Change-Id: I062cc48a151da3ab15b0508f4ebd59d95880ae9a