Migrate CMake to C++14
CMake was officially migrated to require C++11 with fd4fd9a2, which was authored on August 11, 2017, and merged on August 21. This was six years after C++11 was released. The newest standard that was released no less than six years ago at the time of this writing was C++14 (released eight years ago). I am opening this issue to propose requiring C++14 to build CMake so that we can fully take advantage of what it has to offer, and find out if there are any older compilers or systems we want to support that still only support C++11.