Revert "classes.singleton: fix "summary" of singletons. Fixes #145."

This reverts commit d820c86974.

core/classes/singleton/singleton.factor

@@ -1,8 +1,8 @@
 ! Copyright (C) 2008, 2010 Doug Coleman, Slava Pestov.
 ! See http://factorcode.org/license.txt for BSD license.
 USING: classes classes.algebra classes.algebra.private
-classes.predicate classes.predicate.private definitions kernel
-sequences words ;
+classes.predicate classes.predicate.private kernel sequences
+words ;
 IN: classes.singleton
 
 <PRIVATE
@@ -25,7 +25,4 @@ M: singleton-class (classes-intersect?)
     over singleton-class? [ eq? ] [ call-next-method ] if ;
 
 M: singleton-class predicate-quot
-    singleton-predicate-quot ;
-
-M: singleton-class definer
-    drop \ SINGLETON: f ;
+    singleton-predicate-quot ;