isnan.c.patch

diff --git a/missing/isnan.c.orig b/missing/isnan.c
index 5846947..582eb0f 100644
--- a/missing/isnan.c.orig
+++ b/missing/isnan.c
@@ -4,6 +4,7 @@
 
 static int double_ne(double n1, double n2);
 
+#ifndef isnan
 int
 isnan(double n)
 {
@@ -15,3 +16,4 @@ double_ne(double n1, double n2)
 {
     return n1 != n2;
 }
+#endif