Fix for issue #10406: enable Rstrip extension on OSX

Without this patch the Rstrip extension for IDLE is not enabled on OSX,
while it is enabled on other platforms.

Patch by Ned Deily.

Mac/IDLE/config-extensions.def

@@ -86,3 +86,8 @@ bgcolor=LightGray
 fgcolor=Black
 [CodeContext_bindings]
 toggle-code-context=
+
+[RstripExtension]
+enable=1
+enable_shell=0
+enable_editor=1

Misc/NEWS

@@ -18,6 +18,9 @@ Library
 
 - Issue #10107: Warn about unsaved files in IDLE on OSX.
 
+- Issue #10406: Enable Rstrip IDLE extension on OSX (just like on other
+  platforms).
+
 - Issue #10478: Reentrant calls inside buffered IO objects (for example by
   way of a signal handler) now raise a RuntimeError instead of freezing the
   current process.