bpo-41111: xxlimited.c defines Py_LIMITED_API (GH-25151)

xxlimited.c and xxlimited_35.c now define the Py_LIMITED_API macro,
rather than having to do it in the build recipe.

Co-authored-by: Hai Shi <shihai1992@gmail.com>
diff --git a/setup.py b/setup.py
index 3b4e7ae..edf3cb4 100644
--- a/setup.py
+++ b/setup.py
@@ -1865,10 +1865,8 @@ def detect_modules(self):
 ##         self.add(Extension('xx', ['xxmodule.c']))
 
         # Limited C API
-        self.add(Extension('xxlimited', ['xxlimited.c'],
-                           define_macros=[('Py_LIMITED_API', '0x030a0000')]))
-        self.add(Extension('xxlimited_35', ['xxlimited_35.c'],
-                           define_macros=[('Py_LIMITED_API', '0x03050000')]))
+        self.add(Extension('xxlimited', ['xxlimited.c']))
+        self.add(Extension('xxlimited_35', ['xxlimited_35.c']))
 
     def detect_tkinter_fromenv(self):
         # Build _tkinter using the Tcl/Tk locations specified by