Add an SCRef REPR.

This allows an SC to be referenced in an objecty way.

src/org/perl6/nqp/sixmodel/REPRRegistry.java

@@ -39,5 +39,6 @@ public static void setup() {
         addREPR("P6int", new P6int());
         addREPR("P6num", new P6num());
         addREPR("Uninstantiable", new Uninstantiable());
+        addREPR("SCRef", new SCRef());
     }
 }

src/org/perl6/nqp/sixmodel/reprs/SCRef.java

@@ -0,0 +1,23 @@
+package org.perl6.nqp.sixmodel.reprs;
+
+import org.perl6.nqp.runtime.ThreadContext;
+import org.perl6.nqp.sixmodel.REPR;
+import org.perl6.nqp.sixmodel.STable;
+import org.perl6.nqp.sixmodel.SixModelObject;
+import org.perl6.nqp.sixmodel.TypeObject;
+
+public class SCRef extends REPR {
+	public SixModelObject type_object_for(ThreadContext tc, SixModelObject HOW) {
+		STable st = new STable(this, HOW);
+        SixModelObject obj = new TypeObject();
+        obj.st = st;
+        st.WHAT = obj;
+        return st.WHAT;
+	}
+
+	public SixModelObject allocate(ThreadContext tc, STable st) {
+		SCRefInstance obj = new SCRefInstance();
+        obj.st = st;
+        return obj;
+	}
+}

src/org/perl6/nqp/sixmodel/reprs/SCRefInstance.java

@@ -0,0 +1,8 @@
+package org.perl6.nqp.sixmodel.reprs;
+
+import org.perl6.nqp.sixmodel.SerializationContext;
+import org.perl6.nqp.sixmodel.SixModelObject;
+
+public class SCRefInstance extends SixModelObject {
+	public SerializationContext sc;
+}