Add versionadded tag to PySys_FormatStd*() functions doc

Doc/c-api/sys.rst

@@ -118,11 +118,15 @@ accessible to C code.  They all work with the current interpreter thread's
    :cfunc:`PyUnicode_FromFormatV` and don't truncate the message to an
    arbitrary length.
 
+   .. versionadded:: 3.2
+
 .. cfunction:: void PySys_FormatStderr(const char *format, ...)
 
    As :cfunc:`PySys_FormatStdout`, but write to :data:`sys.stderr` or *stderr*
    instead.
 
+   .. versionadded:: 3.2
+
 .. _processcontrol:
 
 Process Control