nghttpd: Use larger write buffer

src/HttpServer.h

@@ -141,7 +141,7 @@ private:
   ev_io rev_;
   ev_timer settings_timerev_;
   std::map<int32_t, std::unique_ptr<Stream>> id2stream_;
-  RingBuf<16384> wb_;
+  RingBuf<65536> wb_;
   std::function<int(Http2Handler &)> read_, write_;
   int64_t session_id_;
   nghttp2_session *session_;