add traceur test suite

test/fixtures/traceur/Classes/ExtendNonConstructableFunction.js

@@ -0,0 +1,11 @@
+
+assert.throw(function() {
+  class C extends Math {}
+}, 'Super expression must either be null or a function');
+
+assert.throw(function() {
+  function f() {}
+  // prototype needs to be an Object or null.
+  f.prototype = 42;
+  class C extends f {}
+}, 'super prototype must be an Object or null');