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/Misc/NEWS b/Misc/NEWS
index c9a0522..354d09a 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@
 Core and Builtins
 -----------------
 
+- Issue #12732: In narrow unicode builds, allow Unicode identifiers which fall
+  outside the BMP.
+
 - Issue #11603: Fix a crash when __str__ is rebound as __repr__.  Patch by
   Andreas Stührk.