Fix a few problems with the huge mpdconf update. There's alot of shift here, mostly due to word wraps. This, also, improves on uniformity and clarity of the document.

"playlistdelete" takes a song position, not a song id.  There are
no song ids in stored playlists.

When save_absolute_paths_in_playlists was enabled in mpd.conf, MPD
broke all playlists when manipulated using the "playlistdelete"
command.  The reason was that map_directory_child_fs() was used, which
doesn't accept slashes in the file name.  Use the new map_uri_fs()
function instead.

With a large maximum playlist length, the integer multiplication
"playlist_max_length * MPD_PATH_MAX" may overflow.  Change that to a
division.  This was not a dangerous bug, since it was only used for
a quick estimate.

The old code casted it to a 32 bit integer, which cut off bits.
AVFormatContext.duration is a int64_t, so use this type.

Use NULL instead.  Found by sparse.

Added missing includes.

Add G_GNUC_UNUSED attributes.

Add a G_GNUC_UNUSED attribute.

Don't distribute the whole scripts/ directory, because this may
include editor backup files and other temporary files.

The m4 files are automatically included in the distribution.

Add separate files.  This fixes "make distcheck".

configure options should use the dash instead of the underscore.

Unix domain socket support is enabled by default.

libmikmod seems to be unmaintained, and has several critical bugs
which make MPD crash.

 http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=461519
 http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=476339

Disable the plugin by default to minimize harm.  Users should
explicitly enable the mikmod decoder (--enable-mod) if they wish to
have it anyway.

It is illegal to pass an empty audio buffer around.  pcm_resample()
sometimes seems to result in 0 samples, maybe related to
libsamplerate.  To work around that problem, add special checks after
both pcm_convert() invocations.  Removed the pcm_resample()==0 checks
from pcm_convert().

When a response is very long (e.g. a large playlist > 100k songs),
most of it will end up in the deferred buffers.  Filling the deferred
queue is very expensive currently, because a new buffer is allocated
for every client_write() operation.  This may lead to long delays, and
the client might give up and disconnect meanwhile.  This patch makes
MPD attempt to flush the deferred queue as often as possible, to work
around this problem.  Due to the MPD 0.14 code freeze, we should not
optimize the buffering code now.

Move the AC_OUTPUT below the checks. So you nicely see what goes wrong.

Conflicts:

	doc/mpdconf.example

Over time mpdconf has evolved and has been maintained and contributed to by many different folks at different
times. Try to give it some unity. Attempt to clear up some language and make things crystal clear. Add more
examples. Use tabs when it makes sense. Make better borders. Remove obsolete options. Try to put more defaults
when it makes sense.

The "user" option does not work if MPD is started by an unprivileged
user.

Make "secure" a log level different from "default".  "secure" should be
right between "default" and "verbose".  Map "default" to Glib's
"MESSAGE" log level.

If lame was not available, the shout_mp3 plugin was enabled anyway,
and triggered compiler errors.

First check if an ecoder plugin is available, then determine whether
to enable the shout output plugin.

getPlayerErrorStr() assumes that pc.errored_song is set when an error
occured.  Since the song may have been deleted meanwhile, add a NULL
check.