Configuration test for working getc_unlocked() (and flockfile() and
funlockfile()).
diff --git a/config.h.in b/config.h.in
index 6b503fe..f7f886b 100644
--- a/config.h.in
+++ b/config.h.in
@@ -97,6 +97,9 @@
 /* Define this if your time.h defines altzone */
 #undef HAVE_ALTZONE
 
+/* Define this if you have flockfile(), getc_unlocked(), and funlockfile() */
+#undef HAVE_GETC_UNLOCKED
+
 /* Define this if you have some version of gethostbyname_r() */
 #undef HAVE_GETHOSTBYNAME_R