cpp14

PR NVIDIA/cub#218 fixes this CUB's radix sort. We should:

• Check whether Thrust's other backends handle this case correctly.
• Provide a guarantee of this in the stable_sort documentation.
• Add regression tests to enforce this on all backends.

When compiling example/device/example_device_radix_sort.cu with

clang++-11 -DTHRUST_IGNORE_CUB_VERSION_CHECK -I../.. --cuda-gpu-arch=sm_61 -std=c++17 -x cuda -c example_device_radix_sort.cu

it errors:

clang: warning: Unknown CUDA version 11.0. Assuming the latest supported version 10.1 [-Wunknown-cuda-version]
In file included from example_device_radix_sort.cu:46:
In file inc

Add Runnable links of the code below the example.
Use link name Run Code which links to a Online C++ complier conatining the example code.
Use Rextester as the Online C++ Compiler (If you have a better suggesstion please comment).

Follow below steps to generate the Run Code Link.

1. Go to Rextester
2. Copy or write the example