workers (as specified in the xml) instead of the one thread per source model.
This affects most files as they tend to interact with a client to some degree
but some of those are in minor ways.

The most significant changes are in :-
- file serving engine. There is no separate thread now, so the client reads
and sends are driven from the worker, this includes the error responses.
- The source client and listener processing. The source client details have
to stay around until the listeners are processed.
- slave engine. relays are always allocated a client on the worker, with a
thread created just for the connection phase. Makes it easier to handle when
switching to another relay source.


svn path=/icecast/branches/kh/icecast/; revision=16219