Issue #13703: add a way to randomize the hash values of basic types (str, bytes, datetime)
in order to make algorithmic complexity attacks on (e.g.) web apps much more complicated.

The environment variable PYTHONHASHSEED and the new command line flag -R control this
behavior.
diff --git a/Include/pythonrun.h b/Include/pythonrun.h
index 96a0e23..af4aa08 100644
--- a/Include/pythonrun.h
+++ b/Include/pythonrun.h
@@ -174,6 +174,8 @@
 PyAPI_FUNC(PyOS_sighandler_t) PyOS_getsig(int);
 PyAPI_FUNC(PyOS_sighandler_t) PyOS_setsig(int, PyOS_sighandler_t);
 
+/* Random */
+PyAPI_FUNC(int) _PyOS_URandom (void *buffer, Py_ssize_t size);
 
 #ifdef __cplusplus
 }