Replace use of deprecated C Standard library headers in C++ code.

Change-Id: I9fa6630c7e4bdb2897df34d417635d8c7d8253bc
Signed-off-by: Tyler Chatow <tchatow@gmail.com>
diff --git a/aos/ftrace.cc b/aos/ftrace.cc
index af4964c..f159a76 100644
--- a/aos/ftrace.cc
+++ b/aos/ftrace.cc
@@ -1,7 +1,7 @@
 #include "aos/ftrace.h"
 
-#include <stdarg.h>
-#include <stdio.h>
+#include <cstdarg>
+#include <cstdio>
 
 namespace aos {