This allows us to do a directory connection *through* tor just
as if we're doing it as an application.

Make ap_conns tolerate it when the application sends stuff before
The socks handshake is done (it just buffers it).

Tell directory_initiate_command the length of the payload (because
it might include nuls).

Add a directory_has_arrived function to, for example, start building
the rendezvous service descriptor.


svn:r1412