Expand .gitignore
Improvements to passive-to-active transition

- l2info can now be set from a synfilter

- altfib can now be set from a synfilter, so the interface the
  syncache responds via during a timeout conversion to active can be
  selected

- SO_PASSIVE for new connections now defaults to the listen socket
  setting (as before) but can be overridden in/by the syncache.

- the INP_INFO lock is now acquired during passive-to-active
  transition on a socket.