Added support for track and disc items in smart playlists

README_SMARTPL.md

@@ -40,6 +40,8 @@ Where valid field-names (with their types) are:
 * `rating` (integer)
 * `year` (integer)
 * `compilation` (integer)
+* `track` (integer)
+* `disc` (integer)
 * `time_added` (date)
 * `time_modified` (date)
 * `time_played` (date)

src/SMARTPL.g

@@ -92,6 +92,8 @@ INTTAG		:	'play_count'
 			|	'rating'
 			|	'year'
 			|	'compilation'
+			|	'track'
+			|	'disc'
 			;
 
 DATETAG		:	'time_added'