Make AP connections wait for a circuit if none exists.

Make AP connections wait for a circuit if none exists.
Also:
  - Refactor socks request into a separate struct
  - Add a separate 'waiting for circuit' state to AP connections
    between 'waiting for socks' and 'open'.

Arma: can you check out the XXX's I've added to connection_edge? I may
be mishandling some async and close logic.

svn:r783