move es6 tail call test

test/core/fixtures/transformation/es6.tail-call/default-parameters/actual.js

@@ -0,0 +1,6 @@
+function sum(a=1, b=2) {
+  if (b > 0) {
+    return sum(a + 1, b - 1);
+  }
+  return a;
+}

test/core/fixtures/transformation/es6.tail-call/default-parameters/expected.js

@@ -0,0 +1,20 @@
+"use strict";
+
+function sum() {
+  var _arguments = arguments;
+  var _again = true;
+
+  _function: while (_again) {
+    a = b = undefined;
+    var a = _arguments[0] === undefined ? 1 : _arguments[0];
+    _again = false;
+    var b = _arguments[1] === undefined ? 2 : _arguments[1];
+
+    if (b > 0) {
+      _arguments = [a + 1, b - 1];
+      _again = true;
+      continue _function;
+    }
+    return a;
+  }
+}