consistently use Py_TYPE, Py_REFCNT, and correct initializer macros (#3563)

This no-op change makes 2.7 more consistent with 3.x to ease comparison and backports.
diff --git a/Modules/_json.c b/Modules/_json.c
index be1e079..39ec467 100644
--- a/Modules/_json.c
+++ b/Modules/_json.c
@@ -1767,8 +1767,7 @@
 
 static
 PyTypeObject PyScannerType = {
-    PyObject_HEAD_INIT(NULL)
-    0,                    /* tp_internal */
+    PyVarObject_HEAD_INIT(NULL, 0)
     "_json.Scanner",       /* tp_name */
     sizeof(PyScannerObject), /* tp_basicsize */
     0,                    /* tp_itemsize */
@@ -2344,8 +2343,7 @@
 
 static
 PyTypeObject PyEncoderType = {
-    PyObject_HEAD_INIT(NULL)
-    0,                    /* tp_internal */
+    PyVarObject_HEAD_INIT(NULL, 0)
     "_json.Encoder",       /* tp_name */
     sizeof(PyEncoderObject), /* tp_basicsize */
     0,                    /* tp_itemsize */