bpo-40170: PyObject_NEW() becomes an alias to PyObject_New() (GH-19379)

The PyObject_NEW() macro becomes an alias to the PyObject_New()
macro, and the PyObject_NEW_VAR() macro becomes an alias to the
PyObject_NewVar() macro, to hide implementation details. They no
longer access directly the PyTypeObject.tp_basicsize member.

Exclude _PyObject_SIZE() and _PyObject_VAR_SIZE() macros from
the limited C API.

Replace PyObject_NEW() with PyObject_New() and replace
PyObject_NEW_VAR() with PyObject_NewVar().
diff --git a/Modules/_curses_panel.c b/Modules/_curses_panel.c
index 77a6a14..7ca91f6 100644
--- a/Modules/_curses_panel.c
+++ b/Modules/_curses_panel.c
@@ -239,7 +239,7 @@
 {
     PyCursesPanelObject *po;
 
-    po = PyObject_NEW(PyCursesPanelObject,
+    po = PyObject_New(PyCursesPanelObject,
                       (PyTypeObject *)(_curses_panelstate_global)->PyCursesPanel_Type);
     if (po == NULL) return NULL;
     po->pan = pan;