Dead link on the Advanced Topics page in the documentation.

The "Advanced Topics" page in the documentation contains a link to a blog post that no longer exists. The link on the page is ["Custom OpenCL functions in C++ with Boost.Compute"](http://kylelutz.blogspot.com/2014/03/custom-opencl-functions-in-c-with.html). If you navigate to that link, you'll see it no longer exists. However, I was able to find the blog post in the Internet Archive: [https://web.archive.org/web/20201112042827/http://kylelutz.blogspot.com/2014/03/custom-opencl-functions-in-c-with.html](https://web.archive.org/web/20201112042827/http://kylelutz.blogspot.com/2014/03/custom-opencl-functions-in-c-with.html).