Clean up after bpo-33738. (GH-7627)

* Add declarations even if they are overridden by macros.
* Make the declaration and the definition of PyExceptionClass_Name
  consistent.
diff --git a/Objects/exceptions.c b/Objects/exceptions.c
index 7beb2a2..e1615b2 100644
--- a/Objects/exceptions.c
+++ b/Objects/exceptions.c
@@ -347,7 +347,7 @@
 char *
 PyExceptionClass_Name(PyObject *ob)
 {
-    return ((PyTypeObject*)ob)->tp_name;
+    return (char *)((PyTypeObject*)ob)->tp_name;
 }
 
 static struct PyMemberDef BaseException_members[] = {