/*
* Add one or more songs to the playlist.
*
* This method raises an Xmms::Error exception if XMMS is not running,
* an ArgumentError exception if the number of arguments is less than 1,
* or a TypeError exception if the argument isn't a String, True, or
* False.
*
* Examples:
* # replace the current playlist with one song
* enqueue = false
* remote.add 'path/to/cool_song.mp3', enqueue
*
* # add several files to the current playlist
* files = %w{song01.mp3 song02.mp3 song03.mp3 song04.mp3 song05.mp3}
* remote.add *files
*
*/
static VALUE xr_pl_add(int argc, VALUE *argv, VALUE self) {