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/sys/vfs.h b/libc/include/sys/vfs.h
index 1a640ba..5d078be 100644
--- a/libc/include/sys/vfs.h
+++ b/libc/include/sys/vfs.h
@@ -29,8 +29,9 @@
 #ifndef _SYS_VFS_H_
 #define _SYS_VFS_H_
 
-#include <stdint.h>
 #include <sys/cdefs.h>
+
+#include <stdint.h>
 #include <sys/types.h>
 
 __BEGIN_DECLS