use std::snprintf for C++11
diff --git a/src/lib_json/json_writer.cpp b/src/lib_json/json_writer.cpp
index f7ad1e2..ef976bf 100644
--- a/src/lib_json/json_writer.cpp
+++ b/src/lib_json/json_writer.cpp
@@ -29,6 +29,8 @@
 
 #if defined(_MSC_VER) && _MSC_VER < 1500 // VC++ 8.0 and below
 #define snprintf _snprintf
+#elif __cplusplus >= 201103L
+#define snprintf std::snprintf
 #endif
 
 #if defined(_MSC_VER) && _MSC_VER >= 1400 // VC++ 8.0