blacksholes njit does not get offloaded to GPU

[reazulhoque]

Reporting a bug

• I have tried using the latest released version of Numba (most recent is
  visible in the change log (https://github.com/numba/numba/blob/master/CHANGE_LOG).
• I have included below a minimal working reproducer (if you are unsure how
  to write one see http://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports).

Example Blacksholes numba/dppl/examples/blacksholes_njit.py does not get offloaded to GPU.

The error seems to be generated from logterm = np.log(sptprice / strike) (line 19).

During the lowering of the parfor in numba/dppl/dppl_lowerer.py(1088), we fail with the following error

ValueError: ctypes objects containing pointers cannot be pickled