libdaemon: Draft logging infrastructure.

libdaemon: Draft logging infrastructure.

- logging is not controlled by "levels" but by "types"; types are
  independent of each other... implementation of the usual "log level"
  user-level semantics can be simply done on top; the immediate
  application is enabling/disabling wire traffic logging independently
  of other debug data, since the former is rather bulky and can easily
  obscure almost everything else
- all logs go to "outlets", of which we currently have 2: syslog and
  stderr; which "types" go to which "outlets" is entirely configurable