Enable C++17 support in build
- Miscellaneous cleanup to CMake
- Add C++17 standard to CMake
- Add cxxopts and cxx recipe for Makefiles
- Add DEVELOP support to CMake
This changes the minimum supported GCC version to 5, MSVC version to VS 2017/MSVC 19.15, and Clang to 5, though does not adjust the Makefiles to "unsupport" GCC<5. Any C++ code compiled and linked dependent on the C++ standard library will introduce libstdc++ as a runtime dependency, but it is not currently a dependency.
Edited by Eidolon