This version dropped support for qt4, meaning that it has to be built
based on qt5. However, it still relies on qwt5 API, while qwt5 is not
compatible with qt5 (support was added in qwt6). Furthermore, it also
relies on qwtplot3d, which does not officially support qt5, although it
seems to build with it.
It is therefore not clear how to build scidavis 2.3.0, as some dependences
still require qt4.