1. Polish variables in EditorWindow extension loading and Tkinter variable code.
2. Add exception handling to EditorWindow Tkinter variable setvar() and getvar() fcns.
3. EditorWindow: remove some unneeded comments.
4. Add a separator to the Options menu
5. extend.txt: describe how to create a menu entry which has no keybinding.

M Bindings.py
M EditorWindow.py
M extend.txt
diff --git a/Lib/idlelib/Bindings.py b/Lib/idlelib/Bindings.py
index af6ec56..b5e90b0 100644
--- a/Lib/idlelib/Bindings.py
+++ b/Lib/idlelib/Bindings.py
@@ -70,6 +70,7 @@
    ]),
  ('options', [
    ('_Configure IDLE...', '<<open-config-dialog>>'),
+   None,
    ]),
  ('help', [
    ('_About IDLE', '<<about-idle>>'),