header composition fix

PJON.h

@@ -392,12 +392,10 @@ limitations under the License. */
        uint8_t new_length = _shared ? (length + (_sender_info ? 9 : 4)) : (length + (_sender_info ? 1 : 0));

        // Compose PJON 1 byte header from internal configuration
        if(header == 0) {
          header |= (_shared ? MODE_BIT : 0);
          header |= (_sender_info ? SENDER_INFO_BIT : 0);
          header |= (_acknowledge ? ACK_REQUEST_BIT : 0);
        }

        header |= (_shared ? MODE_BIT : 0);
        header |= (_sender_info ? SENDER_INFO_BIT : 0);
        header |= (_acknowledge ? ACK_REQUEST_BIT : 0);
        
        if(new_length >= PACKET_MAX_LENGTH) {
          _error(CONTENT_TOO_LONG, new_length);
          return FAIL;