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/syslog.h b/libc/include/syslog.h
index 33979f0..7a594f1 100644
--- a/libc/include/syslog.h
+++ b/libc/include/syslog.h
@@ -56,8 +56,9 @@
 
 #pragma once
 
-#include <stdio.h>
 #include <sys/cdefs.h>
+
+#include <stdio.h>
 #include <stdarg.h>
 
 __BEGIN_DECLS