- Add libstdcpp feature to indicate a platform is providing a libstdc++
implementation ready for use
- The existing cpp feature now only indicates a working C++ toolchain without
libstdc++. (E.g. still useful for the Arduino compatibility layer.)
- Added libstdcpp as required feature were needed
- Added some documentation on C++ on RIOT
On case-insensitive file systems the root Kconfig file clashes with the
kconfig folder where we keep constants and features, producing the
deletion of one of them. This renames the folder to remove the conflict.
