patch 7.4.1437
Problem:    Old system doesn't have isinf() and NAN. (Ben Fritz)
Solution:   Adjust #ifdefs.  Detect isnan() and isinf() functions with
            configure. Use a replacement when missing. (Kazunobu Kuriyama)
diff --git a/src/config.h.in b/src/config.h.in
index dc0e9b2..f8475a1 100644
--- a/src/config.h.in
+++ b/src/config.h.in
@@ -460,3 +460,12 @@
 
 /* Define if GTK+ GUI is to be linked against GTK+ 3 */
 #undef USE_GTK3
+
+/* Define if we have isinf() */
+#undef HAVE_ISINF
+
+/* Define if we have isnan() */
+#undef HAVE_ISNAN
+
+/* Define to inline symbol or empty */
+#undef inline