AC_CHECK_HEADERS defines HAVE_LOCALE_H, so we don't have to manually
define HAVE_LOCALE.

First do the checks for mandatory stuff (libc features, glib,
pkg-config), then all the options.

Don't check for inttypes.h and langinfo.h.

Fix a typo.

Use g_strndup() instead of g_memdup().

Make db_load(), db_save() and db_check() return bool instead of int.

For updating the database, directory_update_init() should be called
explicitly.

It's unused.

The notify library is easier to use, and has no disadvantages.

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

Handle the DELETE and UPDATE events in separate callbacks:
song_delete_event() safely deletes a song, and update_finished_event()
is called when database update is complete.

GLib mandates that you initialize all GError objects with NULL prior
to passing it.

Pass NULL instead of &error to g_convert().  We're not interested in
the error object.

Use GLib's g_build_filename() instead of pfx_dir().

directory_is_root() is cheaper than
isRootDirectory(directory_get_path()).

Don't call command_error() if loading a song from the playlist fails.
This may result in assertion failures, since command_error() may be
called more than once.

The struct delete_data has only one member left and can be eliminated.

Determine the suffix manually, and use decoder_plugin_from_suffix()
and archive_plugin_from_suffix() instead.

This way, song_file_update_inarchive() can be optimized: it does not
have to translate its path.

Newline characters are already checked in skip_path() (update.c).

Don't include headers which are not used.  Fix some includes in
decoder_thread.c.

Reverse the condition: delete directories which don't exist anymore.
This typo caused a slowdown during partial database update.

For internal checks (i.e. not in command.c), we need to check whether
an URI is in the databse, in the local file system or a remote URI
with a scheme.

Check if the URI scheme is supported by MPD, and print an error
message if not.  Optimize the checks in "add" and "playlistadd".

Don't work with argv[1], give it the better name "uri".

libid3tag comes without a pkg-config file, and it is usually added by
distribution packages.  For those without .pc file, attempt to
auto-detect the library with AC_CHECK_LIB.

When the decoder of the new song is not fast enough, the player thread
has to wait for it for a moment.  However the variable "nextChunk" was
reset to -1 during that, making the next loop iteration assume that
cross-fading has not begun yet.  This patch overwrites it with "0"
while waiting.

The icy_metadata will be used by the curl input_stream implementation.

The tag() method reads a tag from the stream.  This replaces the
meta_name and meta_title attributes.

tag_merges() merges the data from two tag objects into one.