In the top-level setup.py, the code to define the Extension instance for the "xxlimited" extension is currently incorrectly located near the end of detect_tkinter() rather than in its parent detect_modules(). This has the effect of skipping the build of "xxlimited" on OS X since detect_tkinter() shortcuts to detect_tkinter_darwin() there.  The attached patch corrects that.

However, it does raise the question of why "xxlimited" is built at all for normal installable builds, since "xxlimited" is a dummy template module.  The definition for the somewhat similar "xx" is commented out by default.  Perhaps "xxlimited" should be as well.  Or perhaps both should only be built for --with-pydebug configs.  Opinions?