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/strings.h b/libc/include/strings.h
index d203bd2..7543edc 100644
--- a/libc/include/strings.h
+++ b/libc/include/strings.h
@@ -43,8 +43,9 @@
  * @brief Extra string functions.
  */
 
-#include <sys/types.h>
 #include <sys/cdefs.h>
+
+#include <sys/types.h>
 #include <xlocale.h>
 
 #include <bits/strcasecmp.h>