added tests for assignable and memory

tests/sprint2/test/test_invalid_recop.alpha

@@ -0,0 +1,10 @@
+type rec: [integer: x; integer: y]
+
+entry(arg) := {
+	[rec: w]
+	w := reserve w;
+	w.x := 1;
+	w.y := 2;
+	w.z := 3;
+        return 0;
+}