Use #pragma omp simd in OpenMP Code

[jbreitbart]

My editor also removed a few trailing whitespaces

[jeffhammond]

I'm sorry that this was not addressed before. The PRK team was busy with a bunch of other things and is still in the process of figuring out our Git(hub) workflow. I will work on this soon.

[jeffhammond]

The whitespace changes makes this pull request impossible, but I will make the changes you propose by hand and acknowledge you in the commit message.

The other issue is that pragma omp simd requires OpenMP 4, which some compilers do not support. To preserve the portability of the PRKs, I am going to do a holistic solution involving C99/C++11 _Pragma as demonstrated in https://github.com/jeffhammond/nwchem-tce-triples-kernels/blob/master/src/pragma_vendor.h.

[jbreitbart]

Sorry, about the whitespaces.