Fix specifying a TCP listen backlog of 0 causing some systems to not accept any incoming connections. Fixes #1369.

src/SFML/Network/TcpListener.cpp

@@ -80,7 +80,7 @@ Socket::Status TcpListener::listen(unsigned short port, const IpAddress& address
     }
 
     // Listen to the bound port
-    if (::listen(getHandle(), 0) == -1)
+    if (::listen(getHandle(), SOMAXCONN) == -1)
     {
         // Oops, socket is deaf
         err() << "Failed to listen to port " << port << std::endl;