winddi.h contains #include <ddrawint.h> and #include <d3dnthal.h> but I cannot find either of these files in mingw svn repository (or in the mingw fedora packages I installed
Its under /experimental/ddk_test for now.
And is it intentional that winddi.h from mingw-w64/trunk/mingw-w64-headers/include/ references headers from experimental/ddk_test?
This issue is caused by the external reference to ROS' svn-repository here. It was always a bad idea (and reason for such broken dependencies) to provide the ddk headers this way. As long as we want trunk being a release-branch, the ddk-headers have to be fixed as they are in 2.x and 1.x branch.
So I suggest to replace svn-external on trunk by the ddk_test version from experimental on trunk. The svn-external should be put just into the experimental tree.
Making the stable branches to use a copy of ddk_test seems to be the right decision, because the upstream r/os repo headers are not usable for us as they are because of the annotations they merged. As for the winddi.h header in question: it just requires the ddk headers to be present from whatever source.
Fixed at revision 4838.