* Add _PyObject_ASSERT_FROM() and _PyObject_ASSERT_FAILED_MSG()
  macros.
* PyObject_GC_Track() now calls _PyObject_ASSERT_FAILED_MSG(),
  instead of Py_FatalError(), if the object is already tracked, to
  dump more information on error.
* _PyObject_GC_TRACK() no longer checks if the object is already
  tracked at runtime, use an assertion instead for best performances;
  PyObject_GC_Track() still checks at runtime.
* pycore_object.h now includes pycore_pystate.h.
* Convert _PyObject_GC_TRACK() and _PyObject_GC_UNTRACK() macros to
  inline functions.