The underlying library has been obsolete for many years.

Track whether _finish() has been called, and deliver all partial
results then.  Fixes Mantis ticket 0003621.

Implements Mantis feature request 3582.

Works around assertion failure in decoder_timestamp().

Implement the "scan_stream" method that can read tags from any
input_stream object.  This requires a FLAC__IOCallbacks implementation
based on the input_stream API.

Improves quality by not squeezing 32 bit samples down to 16 bit, and
then back to 32 bit floating point.  Reduces CPU usage by skipping a
conversion step.

This is necessary for Ogg packets that span more than one page.

We can only check for negative values if the variable is signed.

Implements Mantis ticket 0003340.

Internally the vorbis (non-Tremor) decoder is working in floating
point, and it's not really necessary to cut the output back to 16-bit
if the soundcard or OS supports higher resolution.

The decoder can be trivially modified to bypass its internal
quantisation and produce floating-point output, and a separate
quantisation can be used as appropriate to the platform.

libvorbisidec and libvorbis export the same symbols, which is a
dangerous thing.  Since libvorbisenc depends on libvorbis, this can
get nasty, so let's disable the Vorbis encoder unless the user
explicitly wants it.

WavPack tags are always APEv2, by definition.  Reuse the tag_table
from tag_ape.c, instead of rolling our own.

Using libopus and libogg.

Implements Mantis ticket 0003549.

This commit reimplements the core of the "single" mode.  Instead of
doing the detection in the playlist code from the outside, it is moved
to the player thread, which gets a new option called "border_pause".
It will now pause playback exactly at the beginning of the new song,
making the feature more reliable.

Now that the player thread knows what will happen, it can suppress
cross-fading.

Fixes mantis tickets 0003055 and 0003166.

Use libfluidsynth's new function fluid_player_get_status().

Use fluid_is_midifile() to verify the file format.

The libfluidsynth API is now sane, and does not require real-time
decoding.

Reset the timer when paused and no client is connected.

This fixes Mantis ticket 0003527.

Duplicate the music_dir variable: one encoded in UTF-8, and another
one using the configured filesystem character set.  This fixes an
ancient MPD bug.

That function is not pure, it writes to error.

When marked as pure, the compiler is allowed to assume it does not do
anything to error, so it can remain NULL, which would result in an
invalid read in print_error().

Rewrite of the pc_get_error_message() function, now using a GError
object instead of the complicated "errored_song" attribute.