The macros were moved to "Includes/cpython/", not to "Includes/internal/". That suggests to me that they should use "extern C", so that C++ code that wants to make use of CPython internals can use them.
Basically, the way I see it, *all* header files in "Includes/" and "Includes/cpython/" should work with C++ code and thus have an "extern C". Only the header files in "Includes/internal/" should not have them.
Regardless, I've removed the macro usage from Cython so that the current state doesn't hurt our users.