handle single command and remove hacks used as substitute for it

mpd-git has single command, which provides functionality
of both "repeat one" and "stop after current track" modes.

repeat one = single && repeat
stop after current track = single && !repeat

src/libmpdclient.h

@@ -173,6 +173,8 @@ typedef struct mpd_Status {
 	int repeat;
 	/* 1 if random is on, 0 otherwise */
 	int random;
+	/* 1 if single mode is on, 0 otherwise */
+	int single;
 	/* playlist length */
 	int playlistLength;
 	/* playlist, use this to determine when the playlist has changed */
@@ -520,6 +522,8 @@ void mpd_sendRepeatCommand(mpd_Connection * connection, int repeatMode);
 
 void mpd_sendRandomCommand(mpd_Connection * connection, int randomMode);
 
+void mpd_sendSingleCommand(mpd_Connection * connection, int singleMode);
+
 void mpd_sendSetvolCommand(mpd_Connection * connection, int volumeChange);
 
 /* WARNING: don't use volume command, its depreacted */