player_thread: implement missing "idle" events on output errors

When all outputs fail, MPD automatically pauses playback, but did not
emit the IDLE_PLAYER event.  Thus, clients were not woken up.  (Mantis
3665)
command: allow to omit END in ranges (START:END)

If END is omitted, mpd should use the highest possible value instead of raising an error.
This partially reverts 52e9cab1c1743f64a7
Merge branch 'v0.17.x'