mdnsd v1.2

Changes

• mdnsd: can now run as an unprivileged user. New -u USER and
  -g GROUP options drop privileges after start, and -p FILE places
  the pid file where that user can write it. The bundled systemd unit
  runs unprivileged out of the box, issue #96
• mdnsd: warn, instead of silently note, when -i IFACE cannot filter
  to the interface for lack of the CAP_NET_RAW capability

Fixes

• Fix #97: undefined behavior when caching a name or SRV record with a
  NULL (undecoded) target name, by Julius Pfrommer