symbolic acceptance, cleanup: use .copy() instead of JDD.Ref()

git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@12036 bbc10eb1-c90d-0410-af57-cb519fbb1720

prism/src/acceptance/AcceptanceGenRabinDD.java

@@ -85,8 +85,7 @@ public class AcceptanceGenRabinDD
 		 */
 		public JDDNode getL()
 		{
-			JDD.Ref(L);
-			return L;
+			return L.copy();
 		}
 
 		/** Get the number of K_j sets */
@@ -100,8 +99,7 @@ public class AcceptanceGenRabinDD
 		 */
 		public JDDNode getK(int j)
 		{
-			JDD.Ref(K_list.get(j));
-			return K_list.get(j);
+			return K_list.get(j).copy();
 		}
 
 		/** Returns true if the bottom strongly connected component

prism/src/acceptance/AcceptanceRabinDD.java

@@ -82,8 +82,7 @@ public class AcceptanceRabinDD
 		 */
 		public JDDNode getL()
 		{
-			JDD.Ref(L);
-			return L;
+			return L.copy();
 		}
 
 		/** Get a referenced copy of the state set K.
@@ -91,8 +90,7 @@ public class AcceptanceRabinDD
 		 */
 		public JDDNode getK()
 		{
-			JDD.Ref(K);
-			return K;
+			return K.copy();
 		}
 
 		public RabinPairDD clone()

prism/src/acceptance/AcceptanceStreettDD.java

@@ -83,8 +83,7 @@ public class AcceptanceStreettDD
 		 */
 		public JDDNode getR()
 		{
-			JDD.Ref(R);
-			return R;
+			return R.copy();
 		}
 
 		/** Get a referenced copy of the state set G.
@@ -92,8 +91,7 @@ public class AcceptanceStreettDD
 		 */
 		public JDDNode getG()
 		{
-			JDD.Ref(G);
-			return G;
+			return G.copy();
 		}
 
 		public StreettPairDD clone()