Close #99 增加全局传输限速功能，增加passthrough状态下eventcb的错误日志

* 增加全局传输限速功能，可以限制上游、下游的传输速度；
* 增加eventcb中的错误日志，当BEV_EVENT_ERROR发生时，打印错误代码与日志信息。

platform/include/internal/proxy.h

@@ -46,6 +46,14 @@ struct tfe_proxy_tcp_options
 	int tcp_ttl_downstream;
 };
 
+struct tfe_proxy_rate_limit_options
+{
+	unsigned int read_rate;
+	unsigned int read_burst;
+	unsigned int write_rate;
+	unsigned int write_burst;
+};
+
 struct tfe_proxy_accept_para
 {
 	/* Both upstream and downstream FDs */
@@ -73,6 +81,9 @@ struct tfe_proxy
 	unsigned int nr_work_threads;
 	struct tfe_thread_ctx * work_threads[TFE_THREAD_MAX];
 
+	/* buffer options */
+	unsigned int buffer_output_limit;
+
 	unsigned int nr_modules;
 	struct tfe_plugin * modules;
 
@@ -84,6 +95,10 @@ struct tfe_proxy
 	unsigned int tcp_all_passthrough;
 	struct tfe_proxy_tcp_options tcp_options;
 
+	/* GLOBAL RATELIMIT */
+	unsigned int en_rate_limit;
+	struct tfe_proxy_rate_limit_options rate_limit_options;
+
 	/* PERFOMANCE MONIOTR VARIABLES*/
 	long long stat_val[TFE_STAT_MAX];
 	int fs_id[TFE_STAT_MAX];