完成HTTP请求侧解析调试，可以解析请求的URL。

* 增加插件管理功能（简单实现），可以调用解析层插件；
* 调整HTTP请求侧解析回调函数实现；
* 增加hexdump工具函数；

plugin/protocol/http/include/internal/http_common.h

@@ -32,6 +32,13 @@ struct http_connection_private
 	unsigned int session_id_counter;
 };
 
+enum http_half_status
+{
+	STATUS_INIT,
+	STATUS_READING,
+	STATUS_COMPLETE,
+};
+
 struct http_half_private
 {
 	/* PUBLIC STRUCTURE */
@@ -60,8 +67,9 @@ struct http_half_private
 	struct evbuffer * evbuf_header_value;
 	struct evbuffer * evbuf_body;
 
-	/* STATUS */
-	bool finished;
+	enum http_half_status status_header;
+	enum http_half_status status_body;
+	enum http_half_status status_message;
 };
 
 static inline struct http_half_private * to_hf_request_private(struct http_session_private * hs_private)