Prepend the playlist's base URI to relative song URIs.  Look up songs
in the database (if the URI refers to a local song file).  Merge
existing database metadata with metadata from the playlist plugin.

Added attributes start_ms, end_ms.  This allows us to address a
portion of a song file (important for CUE support).  There is no
support yet for storing these attributes in the state file.

Try the playlist directory first, and if that file does not exist, try
the same relative path within the music directory.

The caller should be responsible for building the absolute URI.

If that fails, try opening the file as a stream.

If there's a slash in the uri_get_suffix() return value, then it's
malformed.  Return NULL in this case.

Remove the data_time parameter from decoder_data().  This patch
eliminates the timestamp counting in most decoder plugins, because the
MPD core will do it automatically by default.

Use the plugin instead of the glue code in normalize.c.  This is used
wrapped inside a "autoconv" filter, to enable normalization for all
input file formats.

Make the audio_format argument non-const.  Allow the open() method to
modify it, to indicate that it wants a different input audio format
than the one specified.  Check that condition in chain_filter_open(),
and fail.

The pcm_volume library supports 32 bit samples, there's no reason to
disallow it in the filter plugin.

Detect misconfiguration during MPD startup, not when playback begins.

Indicate success and error.

This plugin cannot be configured.

Don't close child filters in the filter() method.

This plugin is the groundwork for MPD's future generic CUE sheet
support.  That's not complete yet, e.g. there is no way for a playlist
plugin to address an arbitrary position within a music file.

When no plugin matches the URI scheme, try the file name suffix.

Use open_uri() / open_stream() only after checking that they are
implemented.

Get duration from track_get_length().

Merge code from cue_tag_file() and cue_tag_string().

It's illegal to pass NULL here.  This should not be ignored silently.

Removed the NULL check.

This fixes a NULL pointer dereference in case of archive plugin
failure.

Make archive_file a "real" struct, extended by all plugins.  Add the
plugin pointer to it.  Wrap all method calls in functions.

Moved the archive plugin "extern" declarations into each plugin
header.

Use the raw struct name instead.

Based on libiso9660.

Use g_path_get_basename() instead of manually filtering the path
name.  Big advantage: g_path_get_basename() cannot fail.