http: forward declare json in api

Author: binarytrails

include/opendht/http.h

@@ -34,7 +34,10 @@
 
 #include <memory>
 #include <queue>
-#include <json/json.h>
+
+namespace Json {
+class Value;
+}
 
 extern "C" {
 struct http_parser;

src/http.cpp

@@ -24,6 +24,7 @@
 #include <asio.hpp>
 #include <restinio/impl/tls_socket.hpp>
 #include <http_parser.h>
+#include <json/json.h>
 
 namespace dht {
 namespace http {