This updates the copyright header to all be the same, which is
pretty much an update of where to mail request for a copy of the GPL
and the years of the MPD project. This also puts all committers under
'The Music Player Project' umbrella. These entries should go
individually in the AUTHORS file, for consistancy.

Use GLib's GError library for reporting output device failures.

Note that some init() methods don't clean up properly after a failure,
but that's ok for now, because the MPD core will abort anyway.

The return type of most OS X functions is OSStatus, not int.  We can
get a nice error message from GetMacOSStatusCommentString(), log it.

Don't call AudioOutputUnitStart() in the play() method, do it after
the device has been opened.  We can eliminate the "started" property
now, because the device is always started when it's open.

We don't need to keep commented code forever.  If we want that
test_default_device() implementation back one day, we'll pick it from
the git history.

Renamed types, functions, variables.

audio_output_get_name() has been removed, which was the only function
left in output_api.h.  The output plugin doesn't need the audio_output
object at all, remove the parameter from the init() method.

The meaning of the chunk depends on the audio format; don't suggest a
specific format by declaring the pointer as "char*", pass "void*"
instead.

The old API required an output plugin to not return until all data
passed to the play() method is consumed.  Some output plugins have to
loop to fulfill that requirement, and may block during that.  Simplify
these, by letting them consume only part of the buffer: make play()
return the length of the consumed data.

Now that I've found this nice function in the GLib docs, we can
finally remove our custom sleep function.  Still all those callers of
g_usleep() have to be migrated one day to use events, instead of
regular polling.

Nobody needs these debug messages anymore.

On some platforms, g_free() must be used for memory allocated by
GLib.  This patch intends to correct a lot of occurrences, but is
probably not complete.

All config_get_block_*() functions should accept constant config_param
pointers.

Renamed functions, types, variables.

"#ifdef G_BYTE_ORDER == G_BIG_ENDIAN" cannot work, of course.

Use GLib's G_GNUC_UNUSED instead of gcc.h's mpd_unused.

Remove useless computation. After the pthread_cond_wait loop there are at least MIN(od->bufferSize, size) free bytes in the buffer. Thus MIN(od->bufferSize - od->len, size) is always equal to MIN(od->bufferSize, size).

The OS X output does not seem to support 24 bit audio in the way MPD
implements it currently.  Fall back to 16 bit for now, and schedule
24 bit support on OS X for MPD 0.15.

One my_usleep() invocation remains, until we find out if we can delete
it.

Cast AudioBuffer.mData to a "unsigned char*" before adding "curpos".
This fixes a gcc warning.

Fix prototypes and unused variables.

The OS X output plugin wasn't adapted to the new output plugin yet,
because I had no Mac to test...

Don't return 0/-1 on success/error, but true/false.  Instead of int,
use bool for storing flags.

Don't compile the sources of disabled output plugins at all.

Again, no CamelCase in the directory name.

A frame contains one sample per channel, thus it is sample_size *
channels.  This patch includes some cleanup for various locations
where the sample size for 24 bit audio was still 3 bytes (instead of
4).

The last bit of CamelCase in audio_format.h.  Additionally, rename a
bunch of local variables.

The old struct initializers are error prone and don't allow moving
elements around.  Since we are going to overhaul some of the APIs
soon, it's easier to have all implementations use C99 initializers.

Since the output plugin returns a value indicating success or error,
we can have the output core code assign the "open" flag.

Pass the globally configured audio_format as a const pointer to
plugin.init().  plugin.open() gets a writable pointer which contains
the audio_format requested by the plugin.  Its initial value is either
the configured audio_format or the input file's audio_format.

The inline function audio_format_sample_size() calculates how many
bytes each sample consumes.  This function already takes into account
that 24 bit samples are 4 bytes long, not 3.

Since the plugin struct is never modified, we should store it in
constant locations.

Also rename AudioOutputPlugin to struct audio_output_plugin, and use
forward declarations to reduce include dependencies.