Issue #24330: merge from 3.5

Doc/library/idle.rst

@@ -248,7 +248,8 @@ Configure IDLE
    help sources can be specified.  Non-default user setting are saved in a
    .idlerc directory in the user's home directory.  Problems caused by bad user
    configuration files are solved by editing or deleting one or more of the
-   files in .idlerc.
+   files in .idlerc.  On OS X, open the configuration dialog by selecting
+   Preferences in the application menu.
 
 Configure Extensions
    Open a configuration dialog for setting preferences for extensions

Lib/idlelib/help.txt

@@ -129,7 +129,9 @@ Options Menu (Shell and Editor):
         Configure IDLE -- Open a configuration dialog.  Fonts, indentation,
                           keybindings, and color themes may be altered.
                           Startup Preferences may be set, and additional Help
-                          sources can be specified.
+                          sources can be specified.  On OS X, open the
+                          configuration dialog by selecting Preferences
+                          in the application menu.
 
         ---
         Code Context (toggle) -- Open a pane at the top of the edit window