Close #14309: Deprecate time.clock()

Use time.perf_counter() or time.process_time() instead.
diff --git a/Doc/whatsnew/3.3.rst b/Doc/whatsnew/3.3.rst
index 3d63127..c6708fe 100644
--- a/Doc/whatsnew/3.3.rst
+++ b/Doc/whatsnew/3.3.rst
@@ -1188,6 +1188,9 @@
   the ANSI code page anymore and to support any filename.
 * :issue:`13988`: The :mod:`xml.etree.cElementTree` module is deprecated.  The
   accelerator is used automatically whenever available.
+* The behaviour of :func:`time.clock` depends on the platform: use the new
+  :func:`time.perf_counter` or :func:`time.process_time` function instead,
+  depending on your requirements, to have a well defined behaviour.
 
 
 Deprecated functions and types of the C API