Determination of version information from software build system

[Software build systems can provide version information](https://cmake.org/cmake-tutorial/ "Adding a version number and configured header file") in a structured way.
I suggest to use these data so that [related details like a specific macro](https://github.com/aesophor/Wmderland/blob/e08344fff3a087e064e2a7385abedc0c84933e20/src/config.hpp#L11 "Update candidate: system configuration") will be automatically constructed.