add unit test 229 to verify spork dangling refs

src/test/01-Basic/229-dangle-ref-spork.ck

@@ -0,0 +1,19 @@
+// verify no dangling reference with sporked
+// functions that return Objects
+
+Object foo;
+
+// function that returns an Object
+fun Object get()
+{
+    return foo;
+}
+
+// spork
+spork ~ get();
+
+// give sporked function a chance to run
+10::ms => now;
+
+// check reference count
+if( Machine.refcount(foo) == 1 ) <<< "success" >>>;