Include: change guard of cpython/classobject.h

This aligns it more with other headers in `cpython/` and frees up
the guard for `Include/classobject.h`.

Author: NicolasT

Include/cpython/classobject.h

@@ -3,8 +3,8 @@
 /* Revealing some structures (not for general use) */
 
 #ifndef Py_LIMITED_API
-#ifndef Py_CLASSOBJECT_H
-#define Py_CLASSOBJECT_H
+#ifndef Py_CPYTHON_CLASSOBJECT_H
+#define Py_CPYTHON_CLASSOBJECT_H
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -67,5 +67,5 @@ static inline PyObject* PyInstanceMethod_GET_FUNCTION(PyObject *meth) {
 #ifdef __cplusplus
 }
 #endif
-#endif   // !Py_CLASSOBJECT_H
+#endif   // !Py_CPYTHON_CLASSOBJECT_H
 #endif   // !Py_LIMITED_API