add deprecated warning for loop in async mode

fix sync mode

src/WebSocketsClient.cpp

@@ -340,7 +340,7 @@ void WebSocketsClient::handleClientData(void) {
         switch(_client.status) {
             case WSC_HEADER:
             {
-                String headerLine = _client->tcp->readStringUntil('\n');
+                String headerLine = _client.tcp->readStringUntil('\n');
                 handleHeader(&_client, &headerLine);
             }
                 break;

src/WebSocketsServer.cpp

@@ -98,15 +98,15 @@ void WebSocketsServer::begin(void) {
     DEBUG_WEBSOCKETS("[WS-Server] Server Started.\n");
 }
 
+#if (WEBSOCKETS_NETWORK_TYPE != NETWORK_ESP8266_ASYNC)
 /**
  * called in arduino loop
  */
 void WebSocketsServer::loop(void) {
-#if (WEBSOCKETS_NETWORK_TYPE != NETWORK_ESP8266_ASYNC)
     handleNewClients();
     handleClientData();
-#endif
 }
+#endif
 
 /**
  * set callback function

src/WebSocketsServer.h

@@ -42,7 +42,14 @@ public:
         ~WebSocketsServer(void);
 
         void begin(void);
+#if (WEBSOCKETS_NETWORK_TYPE != NETWORK_ESP8266_ASYNC)
         void loop(void);
+#else
+        // Async interface not need a loop call
+        void loop(void) __attribute__ ((deprecated)) {
+
+        }
+#endif
 
         void onEvent(WebSocketServerEvent cbEvent);