Do not fail with udrec being unknown and say we are using
_GNU_SOURCE. This is needed for the libc/header/gcc combo
fedora 9 is using. bits/socket.h has struct udrec #ifdefed
with _GNU.

Index: dbus-1.0.3/dbus/dbus-sysdeps-unix.c
===================================================================
--- dbus-1.0.3.orig/dbus/dbus-sysdeps-unix.c
+++ dbus-1.0.3/dbus/dbus-sysdeps-unix.c
@@ -22,6 +22,8 @@
  *
  */
 
+#define _GNU_SOURCE
+
 #include "dbus-internals.h"
 #include "dbus-sysdeps.h"
 #include "dbus-sysdeps-unix.h"