Proxied connections to Icecast are now handled with a simple TCP
proxy that can shutdown each direction independently. Fixes some
connection leaks.

Adds detailed information about the transcoding hierarchy and parameters.

Refactor the HTTP handler hierarchy to make it simpler.

Replace the ghost logging handler with a simpler one, that fires as soon
as the HTTP request headers are sent (this is a better solution for
long-lived connections).

Add a debug page to track long-lived HTTP request.

Add tests for the HTTP server.

Adds optional transcoding parameters to a Mount. Each node will then
start a master election for every transcoded stream, and the master will
run liquidsoap to re-encode the data. Transcoding mounts are identical
in other respects to normal mounts, except that liquidsoap acts as a
source for them.

Refactor the load balancing code using a generic traffic control
abstraction that gives the user more control over the final logic (for
the moment this is configured via a command-line parameter).

Introduce node names, allowing a node to have multiple IP addresses.
Also, make the front-end code IPv6-aware and support AAAA records.

This allows running the service on a single port: with the
--enable-icecast-proxy option, all requests can go through
redirectord.