This library crashes on out-of-memory (NULL pointer dereference).
There's not much useful MPD can do in such a situation, so let's
explicitly abort instead, just like GLib does.

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.

Just in case "song" becomes invalid at some point.

Replaces the old global "soundfont" which never worked.

Now that the libfluidsynth API was sanitized, we can enable the plugin
automatically if libfluidsynth is installed.

Use libfluidsynth's new function fluid_player_get_status().

The libfluidsynth now accepts const strings.

Use fluid_is_midifile() to verify the file format.

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

Don't free the string right after calling log_init_file().  Add a new
function log_deinit() that frees the string on shutdown.

This fixes cycling the log file after SIGHUP (Mantis ticket 0003524).

Eliminate the g_usleep() call.

Reduce command latency while paused.

One large loop and only one pa_stream_get_state() call.

Reset the timer when paused and no client is connected.

This fixes Mantis ticket 0003527.

This is part of libavutil.

Additionally, update mpdconf.example to refer to mpd.conf(5) for the
complete list of tags instead of trying to repeat it.

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.

MPD requires GLib 2.16.

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().