Simplify initialization and finalization.

There are numerous race conditions between the libpulse thread
(pulse_mixer.c callbacks) and the rest of MPD.  Protect the volatile
attributes of the pulse_mixer struct with a mutex to fix that.

Eliminate one indent level.  Also remove several debug useless debug
messages.

Those parameters are used after all.

Don't mess with pulse_mixer.volume for setting the volume.  This
variable should only be used to transfer the current volume from
sink_input_vol() to pulse_mixer_get_volume().

The pa_context_get_sink_input_info() function is asynchronous, and
after it returns, libpulse does not guarantee that the operation has
completed yet; in fact, it is not likely.  Explicitly wait for the
operation to complete.

The code for the new pulse_wait_for_operation() function was inspired
by mplayer and xine code.

The function mixer_failed() expects the mixer mutex to be already
locked, yet it calls mixer_close(), which attempts to lock the mutex
again, deadlocking itself.

When single mode is enabled, after current song it stops playback,
or it replay same song if repeat mode is activated.

The smartstop feature is a way to tell mpd to stop playing after
current song.
This patche provides:
- 'state' command returns 'smartstop' state (1 or 0)
- 'smartstop' can activate or not the smartstop state
- when song is terminated, mpd stops playing and smartstop is set to 0

Use the same code style as the rest of MPD.

This patch fixes a longer delay when moving around songs in the
playlist.  The main thread wants to enqueue a new "next" song into the
player thread, but the player thread is waiting inside
audio_output_all_wait() for the output threads.  Use
player_control.notify there, so audio_output_all_wait() gets woken up
by the main thread, too.

The functions playPlaylist() and seekSongInPlaylist() expect a song
position, not a song order number.  Don't convert the "current"
variable with queue_position_to_order().

The move command now accepts a range for the first argument, in the same
form as other range commands, e.g. move 15:17 3.  The first song in the
range is placed at the destination position. Note that as with other
range commands, the range is inclusive on the left only; this example
would move only songs 15 and 16, not 17.

[mk: fixed signed/unsigned warnings; use G_MAXUINT instead of
UINT_MAX]

Clearly specified the format (song1:song2) for range argumentst, and
added the range capability of the playlistinfo command.

moveid uses an index, not a songid, for its second argument

Added g_strerror() and dlopen() suppressions.

Don't initialize attributes which are only used in an open mixer.  As
long as nobody accesses them, their values are uninitialized and
undefined.

The pm->volume attribute was allocated in pulse_mixer_init(), but is
never freed.  This leaks memory.  Instead of adding the g_free() call
to pulse_mixer_finish(), let's just make "volume" a static attribute
of the pulse_mixer struct.  That is easier to deal with.

When the MPD core knows that the pulse mixer is open, pm->mainloop and
pm->context must be non-NULL.

The attributes "online" and "index" were not properly reinitialized
after a close/open cycle.

Nobody needs to modify these strings.  We can make them const, and
convert config_dup_block_string() to config_get_block_string().  This
also fixes memory leaks in the pulse mixer.

The conf.h functions deal well with config_param==NULL and will return
the specified default value then.

When the mixer initialization fails, we have to free the libpulse
objects we have already created, to prevent resource leaks.

It's illegal to return from pulse_mixer_setup() without unlocking the
main loop.  In the error handling, that unlock() call was missing.

Prepare for adding proper error handling.

"volume_set" is an attribute which becomes undefined when the mixer is
closed.  That means, it must be initialized each time the mixer is
opened.

The MPD core guarantees that methods are always invoked in a
consistent state.  This means we can remove lots of checks from the
volume methods.

Instead of replacing NULL with the default device in the open()
method, pass the default device to config_get_block_string().

Use config_get_block_string() instead of config_dup_block_string().

Detect misconfiguration during MPD startup.

The MPD core guarantees that methods are always invoked in a
consistent state.  This means we can remove lots of checks from the
volume methods.

strncasecmp() is locale dependent, but we only need ASCII here.

Instead of replacing NULL with the default path in the open() method,
pass the default path to config_get_block_string().

Use config_get_block_string() instead of config_dup_block_string().

If a (global) mixer has been closed due to failure, don't reopen it
with every volume get/set.  Leave it closed until it is explicitly
opened.

When getting or setting the volume fails, the MPD core close the
mixer.  Moved the duplicated code from the mixer plugins.

Remember if a mixer object is open or closed.  Don't call open() again
if it is already open.  This guarantees that the mixer plugin is
always called in a consistent state, and we will be able to remove
lots of checks from the implementations.

To support mixers which are automatically opened even if the audio
output is still closed (to set the volume before playback starts),
this patch also adds the "global" flag to the mixer_plugin struct.
Both ALSA and OSS set this flag, while PULSE does not.

As a side effect, the previous patch added the mixer==NULL checks.  It
is now illegal to call mixer functions with a NULL argument.  Convert
the runtime checks to assertions.

The mixer core library is now responsible for creating and managing
the mixer object.  This removes duplicated code from the output
plugins.

When the decoder initialization has not been completed yet, all calls
to dc_seek() will fail, because dc.seekable is not initialized yet.
Wait for the decoder to complete its initialization, i.e. until it has
called decoder_initialized().