add getDataAt to RAbstractListVector

com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/data/closures/RAbstactVectorToListClosure.java

@@ -44,6 +44,11 @@ final class RAbstactVectorToListClosure extends RToVectorClosure implements RAbs
         return vector.getDataAtAsObject(index);
     }
 
+    @Override
+    public Object getDataAt(int index) {
+        return vector.getDataAtAsObject(index);
+    }
+
     @Override
     public RList materialize() {
         int length = getLength();

com.oracle.truffle.r.runtime/src/com/oracle/truffle/r/runtime/data/model/RAbstractListVector.java

@@ -37,6 +37,8 @@ public interface RAbstractListVector extends RAbstractVector {
         return getDataAtAsObject(i);
     }
 
+    Object getDataAt(int index);
+
     @Override
     RList materialize();