* The rdc and dlink flags are not required because they are added
  by CMake for separable compilation and static linking respectively
* Add guards around libs that are not included in the CUDA 9.0
  Toolkit
* Only link with OpenMP when linking with cuSOLVER dynamically
* Fix error message when CUDNN is not found

* Address casts from double to __half which are missing in 9.0
* Thrust return_temporary_buffer function can accept void* pointers
  in older versions of Thrust. Use raw_pointer_cast to pass the
  pointer to memFree
* cublasGemmEx doesn't exist in CUDA 9.0. Add ifdefs to guard
  against older builds
* __float2half is not a host function so it needs to be removed
  from mean
* Add template instantiation for memFree to accept void* pointers

CUSOLVER_CHECK error message printed "CUBLAS Error" instead of
CUSOLVER Error