Detach the Song class completely from the public API, only to be used
by SimpleDatabase and the update thread.

From now on, struct Song will be used by the database only, and
DetachedSong will be used by everybody else.  DetachedSong is easier
to use, but Song has lower overhead.

The MPD core takes care for checking the scheme.

Merge some duplicate code.

Replaces GLib's g_str_has_prefix().

Micro-optimization.

Prepare to migrate away from GLib.  Currently, we're still using GLib
as a backend.

Replaces struct playlist_provider.

Use only ConfigData.hxx in plugin sources to reduce header
dependencies.

Replaces GLib's GError.

Fixes build failure on 64 bit.

[mk: backwars compatibility and autoconf check]

Requires YAJL to build, and this doesn't include the necessary
automake changes. Can be built using
./configure CFLAGS="-I/usr/include/yajl" LIBS="-lyajl" --enable-soundcloud

Add the following to your config:

playlist_plugin {
        name "soundcloud"
        enabled "true"
        apikey "c4c979fd6f241b5b30431d722af212e8"
}

Then you can stream from soundcloud using calls like:

mpc load soundcloud://track/<track-id>
mpc load soundcloud://playlist/<playlist-id>
mpc load soundcloud://url/http://soundcloud.com/some/track/or/playlist

For the last case, you can leave off the http:// or
http://soundcloud.com/ .