The 'or' process can now be told (by the global_role variable) what
roles this server should play -- connect to all ORs, listen for ORs,
listen for OPs, listen for APs, or any combination.

* everything in /src/op/ is now obsolete.
* connection_ap.c now handles all interactions with application proxies
* "port" is now or_port, op_port, ap_port. But routers are still always
  referenced (say, in conn_get_by_addr_port()) by addr / or_port. We
  should make routers.c actually read these new ports (currently I've
  kludged it so op_port = or_port+10, ap_port=or_port+20)
* circuits currently know if they're at the beginning of the path because
  circ->cpath is set. They use this instead for crypts (both ways),
  if it's set.
* I still obey the "send a 0 back to the AP when you're ready" protocol,
  but I think we should phase it out. I can simply not read from the AP
  socket until I'm ready.

I need to do a lot of cleanup work here, but the code appears to work, so
now's a good time for a checkin.


svn:r22