$OpenBSD: patch-libs_pbd_fpu_cc,v 1.1 2017/05/25 09:02:05 espie Exp $
upgrade to something that libc++ is happy with

Index: libs/pbd/fpu.cc
--- libs/pbd/fpu.cc.orig
+++ libs/pbd/fpu.cc
@@ -1,4 +1,5 @@
-#define _XOPEN_SOURCE 600
+#define _XOPEN_SOURCE 700
+#define _BSD_SOURCE
 #include <cstdlib>
 #include <stdint.h>
 #include <cstring>
