Syslog output improvements: Fixes #44

The config file location and whether or not we loaded a config
  file from that location are always noted as LOG_INFO (or to
  console...), the zones directory is always mentioned along with
  a count of loaded zonefiles, and the mtime_test warnings explain
  their lack of importance a little better.
reject illegal listen strings of the form ":port"
remove unused am conditional
move GDNSD_DEF_ROOTDIR from config.h to cfg-dirs.h
warn about missing gdnsd user on "make install"
create missing installdirs

In default config, create the base directory for the config
  file, the zones and geoip subdirectores, and the gdnsd rundir
  for the pidfile storage.
In a default-chroot config, create the chroot directory
  (the daemon creates structure within on startup in that case)

Fixes #42
Fix comment text
Do not use IPv6 interfaces from getifaddrs() if IPv6 is broken

Fixes #40