Change equality test to reference comparison for mutable values

test/tests/object comparaison.ans

@@ -0,0 +1,23 @@
+% class
+	:a:b = "foo"
+	:c = "bar"
+
+:o = class
+:a = class
+::b = class
+
+0 = {o == a}
+0 = {o == b}
+1 = {o!constant == b}
+
+~ o.b := "haha"
+
+0 = {o!constant == b}
+
+~ a.b := "haha"
+
+1 = {o!constant == a!constant}
+
+~ o.b := "foo"
+
+0 = {o!constant == b}