in narrow builds, make sure to test codepoints as identifier characters (closes #12732)

This fixes the use of Unicode identifiers outside the BMP in narrow builds.
diff --git a/Lib/test/test_pep3131.py b/Lib/test/test_pep3131.py
index 9d5f217..ed7558a 100644
--- a/Lib/test/test_pep3131.py
+++ b/Lib/test/test_pep3131.py
@@ -8,9 +8,12 @@
             ä = 1
             µ = 2 # this is a compatibility character
             蟒 = 3
+            𝔘𝔫𝔦𝔠𝔬𝔡𝔢  = 4
         self.assertEqual(getattr(T, "\xe4"), 1)
         self.assertEqual(getattr(T, "\u03bc"), 2)
         self.assertEqual(getattr(T, '\u87d2'), 3)
+        v = getattr(T, "\U0001d518\U0001d52b\U0001d526\U0001d520\U0001d52c\U0001d521\U0001d522")
+        self.assertEqual(v, 4)
 
     def test_invalid(self):
         try: