[2.7] bpo-13096: Fix memory leak in ctypes POINTER handling of large values (GH-12100)

Misc/NEWS.d/next/Library/2019-03-04-16-13-01.bpo-13096.SGPt_n.rst

+Fix memory leak in ctypes POINTER handling of large values.

Modules/_ctypes/callproc.c

@@ -1831,6 +1831,7 @@ POINTER(PyObject *self, PyObject *cls)
                                        "s(O){}",
                                        buf,
                                        &PyCPointer_Type);
+        PyMem_Free(buf);
         if (result == NULL)
             return result;
         key = PyLong_FromVoidPtr(result);