skip over tests if :cpu, or :gpu is not available
skip over tests if :cpu, or :gpu is not available

tkelman/OpenCL.jl,JuliaPackageMirrors/OpenCL.jl,yuyichao/OpenCL.jl,yuyichao/OpenCL.jl,JuliaPackageMirrors/OpenCL.jl,tkelman/OpenCL.jl