Add ability to set initial user status.

Setting the status after joining (using the "setstatus" action)
may cause multiple "user" messages to be sent to clients.  Add
the ability to set the initial status at join time.

rtpconn/webclient.go

@@ -1316,9 +1316,20 @@ func handleClientMessage(c *webClient, m clientMessage) error {
 		}
 
 		if c.group != nil {
-			return group.ProtocolError("cannot join multiple groups")
+			return group.ProtocolError(
+				"cannot join multiple groups",
+			)
 		}
 		c.username = m.Username
+		if m.Status != nil {
+			s, ok := m.Status.(map[string]interface{})
+			if !ok {
+				return group.ProtocolError(
+					"bad type for status",
+				)
+			}
+			c.status = s
+		}
 		g, err := group.AddClient(m.Group, c,
 			group.ClientCredentials{
 				Username: m.Username,