Added include for sprintf

AlexeyAB

2018-03-12 15c89e7a714e7e37c13618eace9325a06f0642fc

 src/http_stream.cpp

@@ -37,6 +37,7 @@
#define SOCKET_ERROR   -1
#endif /* _WIN32 */

#include <cstdio>
#include <vector>
#include <iostream>
using std::cerr;