Improve detection of whether tzset is broken.
diff --git a/pyconfig.h.in b/pyconfig.h.in
index dacd304..9df836f 100644
--- a/pyconfig.h.in
+++ b/pyconfig.h.in
@@ -600,6 +600,9 @@
    `tzname'. */
 #undef HAVE_TZNAME
 
+/* Define this if you have tcl and TCL_UTF_MAX==6 */
+#undef HAVE_UCS4_TCL
+
 /* Define this if you have the type uintptr_t. */
 #undef HAVE_UINTPTR_T