Undernet IRC Server Development

* Added +R channel mode, intended to:

  - Allow X to advertise to C that a channel is registered

  - Perhaps eventually allow registered channels to persist without X
    having to be present on the channel at all times

* Removed a "." from /kill messages (to facilitate cut-and-paste)

* IAuth can now properly force-set hostnames and initial user modes

* Add /stats F to report all configured features, not just those
  differing from the default

* OPMODE no longer checks the total ban length and count

* Correct bugs in parsing oplevels received from clients and servers,
  and forward oplevels for all channels that use them

* Extension query system, enabling IAuth to communicate to network
  services as needed (one possible application: login-on-connect)

* Only show silence lists belonging to the user or to +k users
  (channel services), to help keep other clients' servers hidden

* Various G-line related fixes and improvements

* Removal of extraneous assert() calls and clean-ups in network
  engines

* Bug fixes in detection of network loops and L-line and H-line
  checks, to provide better diagnostic messages

* Bug fixes and code clean-ups in delayed join logic