make bytes(o) respect __bytes__ #2415

This adds two new C-API functions: PyObject_Bytes and PyBytes_FromObject.

Reviewer: Barry
diff --git a/Include/object.h b/Include/object.h
index 372eada..60584a0 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -423,6 +423,7 @@
 PyAPI_FUNC(PyObject *) PyObject_Repr(PyObject *);
 PyAPI_FUNC(PyObject *) PyObject_Str(PyObject *);
 PyAPI_FUNC(PyObject *) PyObject_ASCII(PyObject *);
+PyAPI_FUNC(PyObject *) PyObject_Bytes(PyObject *);
 PyAPI_FUNC(int) PyObject_Compare(PyObject *, PyObject *);
 PyAPI_FUNC(PyObject *) PyObject_RichCompare(PyObject *, PyObject *, int);
 PyAPI_FUNC(int) PyObject_RichCompareBool(PyObject *, PyObject *, int);