Add check for rint() in math library.
diff --git a/config.h.in b/config.h.in
index ce254b8..bbe3490 100644
--- a/config.h.in
+++ b/config.h.in
@@ -381,6 +381,9 @@
 /* Define if you have the readlink function.  */
 #undef HAVE_READLINK
 
+/* Define if you have the rint function.  */
+#undef HAVE_RINT
+
 /* Define if you have the select function.  */
 #undef HAVE_SELECT