Completely get rid of PyClass and PyInstance.

(classobject.[ch] aren't empty yet because they also define PyMethod.)
This breaks lots of stuff, notably cPickle. But it's a step in the right
direction. I'll clean it up later.
(Also a few unrelated changes, e.g. T_NONE to define a "struct member"
that is always None, and simplification of __hash__ -- these are unfinished.)

Python/structmember.c

@@ -126,6 +126,10 @@ PyMember_GetOne(const char *addr, PyMemberDef *l)
 		v = PyLong_FromUnsignedLongLong(*(unsigned PY_LONG_LONG *)addr);
 		break;
 #endif /* HAVE_LONG_LONG */
+        case T_NONE:
+		v = Py_None;
+		Py_INCREF(v);
+		break;
 	default:
 		PyErr_SetString(PyExc_SystemError, "bad memberdescr type");
 		v = NULL;