MacOS does not support clang -fopenmp

[chuckcoleman]

I used install.packages("codetools") to install the parallel version to get the error "clang: error: unsupported option '-fopenmp'" LLVM has posted a fix for this at http://blog.llvm.org/2015/05/openmp-support_22.html. It will require making the installation code aware of its environment and acting accordingly.