PEP 466: backport persistent urandom fd (closes #21305)

Patch from Alex Gaynor.
diff --git a/Include/pythonrun.h b/Include/pythonrun.h
index c319c52..57ef2bb 100644
--- a/Include/pythonrun.h
+++ b/Include/pythonrun.h
@@ -145,6 +145,7 @@
 PyAPI_FUNC(void) PyFloat_Fini(void);
 PyAPI_FUNC(void) PyOS_FiniInterrupts(void);
 PyAPI_FUNC(void) PyByteArray_Fini(void);
+PyAPI_FUNC(void) _PyRandom_Fini(void);
 
 PyAPI_DATA(PyThreadState *) _Py_Finalizing;