Improve C++ stub headers for cstdarg

Author: lcartey

cpp/common/test/includes/standard-library/cstdarg

@@ -1,9 +1,9 @@
 #pragma once
+#ifndef _GHLIBCPP_CSTDARG
+#define _GHLIBCPP_CSTDARG
+#include "stdarg.h"
 
 namespace std {
-    typedef __builtin_va_list va_list;
+using ::va_list;
 } // namespace std
-
-#define va_arg(v, p) __builtin_va_arg(v, p)
-#define va_end(v) __builtin_va_end(v)
-#define va_start(v,l)  __builtin_va_start(v,l)
+#endif // _GHLIBCPP_CSTDARG

cpp/common/test/includes/standard-library/stdarg.h

@@ -0,0 +1,6 @@
+
+typedef __builtin_va_list va_list;
+#define va_arg(v, p) __builtin_va_arg(v, p)
+#define va_end(v) __builtin_va_end(v)
+#define va_start(v, l) __builtin_va_start(v, l)
+#define va_copy(d, s) __builtin_va_copy(d, s)