GCC Finishing Up C++17 Adjustments, Preparing For C++2A

While C++17 was just formally approved days ago and is now waiting for ISO publication, GCC (and Clang) developers have largely finished up their C++17 (formerly known as "C++1z") support for some time. There are just a few lingering patches for GCC and already are beginning to lay the ground work for C++2a...