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_CHECK_VERSION() instead of manually checking
GLIB_MAJOR_VERSION, ...

Print the list of suffixes supported by each decoder, instead of
prining a list of all suffixes of all decoders with duplicates.

Renamed functions, types, variables.

mpd uses some additional files to work, such as pid_file, state_file,
db_file, etc. when running mpd as non-root user, it is often that those
files end in ~/.mpd

in that case, we end up with 2 entries in a user's home, .mpdconf and
.mpd - which clutters homedirs.

this patch allows ~/.mpd/mpd.conf as an alternative to ~/.mpdconf,
allowing for a cleaner homedir

Start the daemon after --create-db.  This makes --create-db a flag
which discards the old database and starts with a fresh one.

Don't start the daemon when MPD is called with "--version".

Only include headers which are really needed.  os_compat.h aimed to
make MPD easily portable, but was never actually made portable.

Removed the "error_file" option.  There is only one log file now.  If
a user wants to see only the errors, he should configure a log_level.

Build the path with g_build_filename().  Also use g_get_home_dir() and
g_file_test().

Eliminate duplicated code.  The GLib code is much more mature than
MPD's custom parser.

Prepare for the migration to the GLib option parser, which uses
gboolean for flags.