- Allow specification of the location of the OpenCL library on the cmake
configure line (e.g. cmake -DOpenCL_ROOT_DIR=/opt/AMDAPP source_dir)
- Have FindOpenCL.cmake piggy back on find_package(CUDA). On a lot of
machines this will find the NVIDIA OpenCL implementation.
Check whether the AMDAPPSDKROOT environment variable is set. If CUDA
isn't found and this environment variable is set than cmake will search
here for the OpenCL library.