Make the Py<type>_Check() macro use PyObject_TypeCheck().

Include/stringobject.h

@@ -51,7 +51,7 @@ typedef struct {
 
 extern DL_IMPORT(PyTypeObject) PyString_Type;
 
-#define PyString_Check(op) ((op)->ob_type == &PyString_Type)
+#define PyString_Check(op) PyObject_TypeCheck(op, &PyString_Type)
 
 extern DL_IMPORT(PyObject *) PyString_FromStringAndSize(const char *, int);
 extern DL_IMPORT(PyObject *) PyString_FromString(const char *);

Include/tupleobject.h

@@ -26,7 +26,7 @@ typedef struct {
 
 extern DL_IMPORT(PyTypeObject) PyTuple_Type;
 
-#define PyTuple_Check(op) ((op)->ob_type == &PyTuple_Type)
+#define PyTuple_Check(op) PyObject_TypeCheck(op, &PyTuple_Type)
 
 extern DL_IMPORT(PyObject *) PyTuple_New(int size);
 extern DL_IMPORT(int) PyTuple_Size(PyObject *);

Include/unicodeobject.h

@@ -372,7 +372,7 @@ typedef struct {
 
 extern DL_IMPORT(PyTypeObject) PyUnicode_Type;
 
-#define PyUnicode_Check(op) (((op)->ob_type == &PyUnicode_Type))
+#define PyUnicode_Check(op) PyObject_TypeCheck(op, &PyUnicode_Type)
 
 /* Fast access macros */
 #define PyUnicode_GET_SIZE(op) \