Add todo item about hash randomization.

Doc/whatsnew/3.3.rst

@@ -1100,6 +1100,8 @@ that may require changes to your code.
 Porting Python code
 -------------------
 
+.. XXX add a point about hash randomization and that it's always on in 3.3
+
 * :issue:`12326`: On Linux, sys.platform doesn't contain the major version
   anymore. It is now always 'linux', instead of 'linux2' or 'linux3' depending
   on the Linux version used to build Python. Replace sys.platform == 'linux2'