when the initial data is larger than one MTU,
      e.g. HTTP GETs with large URLs, CGI params or cookies,
      or large HTTP POSTS:
      - Don't reject additional packets received without a
        send stream ID (i.e. sent before the SYN ACK was received)
      - Put unknown non-SYN packets on the SYN queue also
        so they won't be rejected
      - Reduce flusher delay to 250ms (was 500)
      - Flush unless window is full (was window is non-empty)