Fix shfl_down warnings with cuda 9

[umar456]

No description provided.

[umar456]

The failures are unrelated to this change.

[pavanky]

Looks good. But double check the performance as well.

[umar456]

Before

ArrayFire v3.6.0 (CUDA, 64-bit Mac OSX, build c78c0d6)
Platform: CUDA Toolkit 9, Driver: CUDA Driver Version: 9010
[0] GeForce GT 750M, 2048 MB, CUDA Compute 3.0
device:  0.02323 seconds to estimate  pi = 3.14140
  host:  0.26709 seconds to estimate  pi = 3.14171

After

ArrayFire v3.6.0 (CUDA, 64-bit Mac OSX, build c78c0d6)
Platform: CUDA Toolkit 9, Driver: CUDA Driver Version: 9010
[0] GeForce GT 750M, 2048 MB, CUDA Compute 3.0
device:  0.02253 seconds to estimate  pi = 3.14140
  host:  0.26195 seconds to estimate  pi = 3.14171

[biswajitcsecu]

ArrayFire v3.6.0 (CUDA, 64-bit Mac OSX, build c78c0d6)
Platform: CUDA Toolkit 9,0

libnvrtc.so.9.1: cannot open shared object file: No such file or directory

[9prady9]

@biswajitcsecu Please make sure you had everything in order as per this Using on OSX tutorial. Also, often so file not found errors are related to missing relevant path($AF_PATH/lib here) in DYLD_LIBRARY_PATH (OSX) or LD_LIBRARY_PATH(Linux).

[biswajitcsecu]

Thank you quick reply. Although I tried before your suggestion and It was solved while I reconfigured my system with CUDA 9.1.