Always include <sys/cdefs.h> first.

Otherwise you can't be sure that things like __BIONIC__ work.

Change-Id: Ic5e59988b69419828c3b1a97332c7e2ab58e09a1
diff --git a/libc/include/arpa/inet.h b/libc/include/arpa/inet.h
index f00f2c1..ce9dd93 100644
--- a/libc/include/arpa/inet.h
+++ b/libc/include/arpa/inet.h
@@ -29,9 +29,10 @@
 #ifndef _ARPA_INET_H_
 #define _ARPA_INET_H_
 
+#include <sys/cdefs.h>
+
 #include <netinet/in.h>
 #include <stdint.h>
-#include <sys/cdefs.h>
 #include <sys/types.h>
 
 __BEGIN_DECLS