client: add Start2; deprecate Start (#801)

examples/proxy-backchannel/client.go

@@ -48,18 +48,20 @@ func (c *client) run() {
 }
 
 func (c *client) read() error {
-	rc := gortsplib.Client{
-		RequestBackChannels: true,
-	}
-
 	// parse URL
 	u, err := base.ParseURL(existingStream)
 	if err != nil {
 		return err
 	}
 
+	rc := gortsplib.Client{
+		Scheme:              u.Scheme,
+		Host:                u.Host,
+		RequestBackChannels: true,
+	}
+
 	// connect to the server
-	err = rc.Start(u.Scheme, u.Host)
+	err = rc.Start2()
 	if err != nil {
 		return err
 	}