[vtk-developers] Add pugixml to VTK

[Utkarsh Ayachit]

> I thought Ben Boeckel was working on a removing as many things from ThirdParty as possible (and making them parts of a superbuild). So perhaps the CityGML reader should live in a VTK module that requires an external pugi? I know pugi is small, but...

I am not sure that's correct. He was doing that for Python 3rd party
modules. Are you referring to that?