Thanks for the review, Terry. The reasons for moving the menders changes are two.  As noted in the comments, the menudefs were being customized early in IDLE initialization before calling Tk to create the root object and, therefore, we did not know at that point which kind of Tk we were running under.  To properly customize, we need to know that, as we are now more careful to customize menus depending on the OS X Tk variant.  Also, there already were other menu customizations being done in macosxSupport; now it is all in one place. It would be nice to reduce the fragility in the menu management. I would encourage anyone interested in working on IDLE to tackle it as a separate issue.

Applied for release in 3.5.0, 3.4.1, and 2.7.7.