Remove all other uses of the C tolower()/toupper() which could break with a Turkish locale.
(except in the strop module, which is deprecated anyway)
diff --git a/Modules/_tkinter.c b/Modules/_tkinter.c
index 01d6284..40c8be2 100644
--- a/Modules/_tkinter.c
+++ b/Modules/_tkinter.c
@@ -663,8 +663,8 @@
     }
 
     strcpy(argv0, className);
-    if (isupper(Py_CHARMASK(argv0[0])))
-        argv0[0] = tolower(Py_CHARMASK(argv0[0]));
+    if (Py_ISUPPER(Py_CHARMASK(argv0[0])))
+        argv0[0] = Py_TOLOWER(Py_CHARMASK(argv0[0]));
     Tcl_SetVar(v->interp, "argv0", argv0, TCL_GLOBAL_ONLY);
     ckfree(argv0);