We now use the generic <DUMMY> hack to avoid duplicate extern "C" symbols.
See rust-lang/rust#26201.
py_module_initializer!() calls now need to manually concatenate the module
name with the prefixes "init" and "PyInit_".
Since the `Python` token no longer is a part of `PyObject`,
lots of methods now require the token as additional argument.
This [breaking-change] breaks everything!
Daniel Grunwald