MEDIUM: stream/trace: Register a new trace source with its events

MEDIUM: stream/trace: Register a new trace source with its events

Runtime traces are now supported for the streams, only if compiled with
debug. process_stream() is covered as well as TCP/HTTP analyzers and filters.

In traces, the first argument is always a stream. So it is easy to get the info
about the channels and the stream-interfaces. The second argument, when defined,
is always a HTTP transaction. And the third one is an HTTP message. The trace
message is adapted to report HTTP info when possible.