- added comments about why in6p_inputopts should not be copied in   tcp6_input(). - call ip6_copypktopts() in order to copy in6p_outputopts   from a listening PCB to a corresponding accepting one.
- added comments about why in6p_inputopts should not be copied in
  tcp6_input().
- call ip6_copypktopts() in order to copy in6p_outputopts
  from a listening PCB to a corresponding accepting one.

MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame