Fix failure to handle SSH_MSG_EXTENDED_DATA.

I left this message type code out of the list in the outer switch in
ssh2_connection_filter_queue for messages with the standard handling
of an initial recipient channel id. The inner switch had a perfectly
good handler for extended data, but the outer one didn't pass the
message on to that handler, so it went back to the main coroutine and
triggered a sw_abort for an unexpected packet.

ssh2connection.c

@@ -626,6 +626,7 @@ static int ssh2_connection_filter_queue(struct ssh2_connection_state *s)
             break;
 
           case SSH2_MSG_CHANNEL_DATA:
+          case SSH2_MSG_CHANNEL_EXTENDED_DATA:
           case SSH2_MSG_CHANNEL_WINDOW_ADJUST:
           case SSH2_MSG_CHANNEL_REQUEST:
           case SSH2_MSG_CHANNEL_EOF: