release v0.19.17

This is required if a stream ands without another chained FLAC file.

It's always 0.

If the duration is unknown, pass SignedSongTime::Negative(), as
documented for decoder_initialized().

This is obsolete because it has been moved to the MPD core.

Referencing the attribute "partition" is illegal after Close(),
because Close() deletes "this".

Fixes use-after-free bug (https://bugs.musicpd.org/view.php?id=4548).

The "seeking" flag is not set for the initial seek, and so
decoder_read() could be canceled when another SEEK was emitted during
initial seek.

This fixes several seek problems, for example the one reported for the
FLAC decoder plugin:

 https://bugs.musicpd.org/view.php?id=4552

libFLAC API documentation suggests that FLAC__stream_decoder_flush()
should be called to recover from FLAC__STREAM_DECODER_SEEK_ERROR.

Stop after all fatal errors.  This fixes assertion failures in
libFLAC.

No change for regular PCM, but DSD uses 0x69 now.

Fixes abort after seeking on fast machines.

Commit 3a212412 changed the meaning of out_audio_format, but I forgot
to apply this to ConvertFilter::FilterPCM().

See https://bugs.musicpd.org/view.php?id=4551

The latter doesn't exist, and this broke Vorbis-only builds.