PyObject_Dump(): New function that is useful when debugging Python's C
runtime.  In something like gdb it can be a pain to get some useful
information out of PyObject*'s.  This function prints the str() of the
object to stderr, along with the object's refcount and hex address.

PyGC_Dump(): Similar to PyObject_Dump() but knows how to cast from the
garbage collector prefix back to the PyObject* structure.

[See Misc/gdbinit for some useful gdb hooks]

none_dealloc(): Rather than SEGV if we accidentally decref None out of
existance, we assign None's and NotImplemented's destructor slot to
this function, which just calls abort().