update the spec wrt choosing aci's

         open a new connection to that router.

      3. Choose an ACI not already in use on the connection with the

         first router in the chain.  If our address/port pair is

         numerically higher than the address/port pair of the other

         side, then let the high bit of the ACI be 1, else 0.

         first router in the chain.  If we are an onion router and our

         nickname is lexicographically greater than the nickname of the

         other side, then let the high bit of the ACI be 1, else 0.

      4. Send a CREATE cell along the connection, to be received by

         the first onion router.

   When an onion router receives an EXTEND relay cell, it sends a

   CREATE cell to the next onion router, with the enclosed onion skin

   as its payload.  The initiating onion router chooses some random

   ACI not yet used on the connection between the two onion routers.

   as its payload.  The initiating onion router chooses some ACI not

   yet used on the connection between the two onion routers.  (But see

   section 4.3. above, concerning choosing ACIs.)

   As an extension (called router twins), if the desired next onion

   router R in the circuit is down, and some other onion router R'