Changes to enable Windows build

[cegbertOculus]

changes to Python.h fixes:
magnum-bindings\src\Magnum/SceneGraph/Python.h(67): error C2614: 'Magnum::SceneGraph::PyObjectesp::scene::SceneNode': illegal member initialization: 'Object' is not a base or member

change to magnum.cpp fixes:
magnum-bindings\src\python\magnum\magnum.cpp(220): error C2375: 'PyInit__magnum': redefinition; different linkage

change to glfw.cpp fixes:
magnum-bindings\src\python\magnum\platform\glfw.cpp(44): error C3640: 'magnum::platform::glfw::PublicizedApplication::[thunk]: __thiscall void __cdecl magnum::platform::glfw(pybind11::module &)'::2'::PublicizedApplication::`vcall'{8,{flat}}' }'': a referenced or virtual member function of a local class must be defined

[mosra]

Hi, thank you for the continued push on Windows support!

This is something I didn't even try for the bindings repo yet. I need to set up a Windows CI job to ensure it builds and continues to build there.

For the first thing, is it possible that Object is some silly macro defined in windows.h? :)

[cegbertOculus]

Yes, I think that's the case, though I couldn't find the source of the problem. The errors I was getting referencing 'Object' weren't really making sense, so I just changed the name to Obj.

[mosra]

Finally had the time to set up a Windows CI. Merged the second and third fix as e8198cb and 14fa224. The Object rename was not needed, but also Magnum is not including windows.h that much anymore, so maybe that fixed it.

Can you confirm current master works for you? Thanks a lot!

[mosra]

Based on private discussion, the C2614-related change was unfortunately really needed as well, comitted as d6f1c50.