bpo-39573: Use Py_TYPE() macro in Objects directory (GH-18392)

Replace direct access to PyObject.ob_type with Py_TYPE().
diff --git a/Objects/floatobject.c b/Objects/floatobject.c
index ab486d4..26e238c 100644
--- a/Objects/floatobject.c
+++ b/Objects/floatobject.c
@@ -256,7 +256,7 @@
             return val;
         }
         PyErr_Format(PyExc_TypeError, "must be real number, not %.50s",
-                     op->ob_type->tp_name);
+                     Py_TYPE(op)->tp_name);
         return -1;
     }
 
@@ -268,7 +268,7 @@
         if (!PyFloat_Check(res)) {
             PyErr_Format(PyExc_TypeError,
                          "%.50s.__float__ returned non-float (type %.50s)",
-                         op->ob_type->tp_name, res->ob_type->tp_name);
+                         Py_TYPE(op)->tp_name, Py_TYPE(res)->tp_name);
             Py_DECREF(res);
             return -1;
         }
@@ -276,7 +276,7 @@
                 "%.50s.__float__ returned non-float (type %.50s).  "
                 "The ability to return an instance of a strict subclass of float "
                 "is deprecated, and may be removed in a future version of Python.",
-                op->ob_type->tp_name, res->ob_type->tp_name)) {
+                Py_TYPE(op)->tp_name, Py_TYPE(res)->tp_name)) {
             Py_DECREF(res);
             return -1;
         }