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().

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

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

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.

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().

Ignore APE tags that have no usable tags, and use the ID3 tag instead.
This is useful when the APE tag only contains replay gain, and the
real tags are stored as ID3.  This implements feature request Mantis
#0003521.

These two strings are common "FILE" types.

No, really!  This fixes a regression of commit 74617389, which
changed the order of filter plugins.