Closes #16732: move "xxmodule" comment block to detect_modules(). (Already done in 3.x)

setup.py

@@ -1721,6 +1721,10 @@ class PyBuildExt(build_ext):
         if '_tkinter' not in [e.name for e in self.extensions]:
             missing.append('_tkinter')
 
+##         # Uncomment these lines if you want to play with xxmodule.c
+##         ext = Extension('xx', ['xxmodule.c'])
+##         self.extensions.append(ext)
+
         return missing
 
     def detect_tkinter_darwin(self, inc_dirs, lib_dirs):
@@ -1911,10 +1915,6 @@ class PyBuildExt(build_ext):
                         )
         self.extensions.append(ext)
 
-##         # Uncomment these lines if you want to play with xxmodule.c
-##         ext = Extension('xx', ['xxmodule.c'])
-##         self.extensions.append(ext)
-
         # XXX handle these, but how to detect?
         # *** Uncomment and edit for PIL (TkImaging) extension only:
         #       -DWITH_PIL -I../Extensions/Imaging/libImaging  tkImaging.c \