In the words of the original author, it was 'crappy'.  I tend to
agree :)

The code has also been broken for at least the past few months,
and nobody bothered fixing it

The previous format it was overly complex: 5 lines to describe
each device.  The new format is one-line per-device:

audio_device_state:%d:%s

%d - 0 for disabled, any integer for enabled
%s - name of the device as specified in the config file,
whitespace and all

Incompatibilities:

* Output names are now _required_ to be unique.

This is required because the new format relies solely on the
name of the audio device.

Relying on the device IDs internal to MPD was a bad idea
anyways since the user usually has none or very little idea
how they're generated, and adding a new device or removing
one from a config would throw things off completely.

This is also just a Good Idea(TM) because it makes things
less confusing to users when they see it in their clients.

* Output states are not preserved from the previous format.

Not a big deal, since the previous code was never officially
released.  Also, it's been broken for months now, so I doubt
anybody would notice :)

git-svn-id: https://svn.musicpd.org/mpd/trunk@3928 09075e82-0dd4-0310-85a5-a0d7c8717e4f