The first commit adds the entries the menu and the second commit grays out the entries when the shell is initially opened.

Some observations:

• I thought about calling the menu items 'Previous Command' and 'Next Command' instead of using the word 'history'.
• When a shell is restarted, the history isn't cleared.
• Should there be a menu item to clear history on demand?
• The history is always cyclic unless someone edits their config file by hand. Since it's not on configdialog to set it, I enable both menu entries whenever there is any history (since, when cyclic, there is always a Previous and Next entry). I think enabling the menu entries when the cyclic flag is False would best be handled at the time cyclic is added the condigdialog.
• I added a new function to editor.py to update the state for the menu items. Because of this, I changed the recently added code for enabling/disabling the Code Context menu item to use this new function.

https://bugs.python.org/issue28097