Streamline tests for Date.prototype.toGMTString

Introduce a test that asserts the equality of
`Date.prototype.toGMTString` and `Date.prototype.toUTCString`, rendering
further tests for the former's behavior unnecessary.

test/annexB/built-ins/Date/prototype/toGMTString/B.2.6.propertyCheck.js

-// Copyright 2009 the Sputnik authors.  All rights reserved.
-// This code is governed by the BSD license found in the LICENSE file.
-
-/*---
-info: Check type of various properties
-es5id: B.2.6
-description: Checking properties of the Date object (toGMTString)
----*/
-
-if (typeof Date.prototype.toGMTString !== "function")  $ERROR('#1: typeof Date.prototype.toGMTString === "function". Actual: ' + (typeof Date.prototype.toGMTString ));
-if (typeof Date.prototype['toGMTString'] !== "function")  $ERROR('#2: typeof Date.prototype["toGMTString"] === "function". Actual: ' + (typeof Date.prototype["toGMTString"] ));

test/annexB/built-ins/Date/prototype/toGMTString/length.js

-// Copyright (C) 2015 André Bargull. All rights reserved.
-// This code is governed by the BSD license found in the LICENSE file.
-
-/*---
-es6id: B.2.4.3
-description: >
-  Date.prototype.toGMTString.length is 0.
-info: >
-  Date.prototype.toGMTString ( )
-
-  17 ECMAScript Standard Built-in Objects:
-    Every built-in Function object, including constructors, has a length
-    property whose value is an integer. Unless otherwise specified, this
-    value is equal to the largest number of named arguments shown in the
-    subclause headings for the function description, including optional
-    parameters. However, rest parameters shown using the form “...name”
-    are not included in the default argument count.
-
-    Unless otherwise specified, the length property of a built-in Function
-    object has the attributes { [[Writable]]: false, [[Enumerable]]: false,
-    [[Configurable]]: true }.
-includes: [propertyHelper.js]
----*/
-
-assert.sameValue(Date.prototype.toGMTString.length, 0);
-
-verifyNotEnumerable(Date.prototype.toGMTString, "length");
-verifyNotWritable(Date.prototype.toGMTString, "length");
-verifyConfigurable(Date.prototype.toGMTString, "length");

test/annexB/built-ins/Date/prototype/toGMTString/name.js

-// Copyright (C) 2015 André Bargull. All rights reserved.
-// This code is governed by the BSD license found in the LICENSE file.
-
-/*---
-es6id: B.2.4.3
-description: >
-  Date.prototype.toGMTString.name is "toUTCString".
-info: >
-  Date.prototype.toGMTString ( )
-
-  17 ECMAScript Standard Built-in Objects:
-    Every built-in Function object, including constructors, that is not
-    identified as an anonymous function has a name property whose value
-    is a String.
-
-    Unless otherwise specified, the name property of a built-in Function
-    object, if it exists, has the attributes { [[Writable]]: false,
-    [[Enumerable]]: false, [[Configurable]]: true }.
-includes: [propertyHelper.js]
----*/
-
-assert.sameValue(Date.prototype.toGMTString.name, "toUTCString");
-
-verifyNotEnumerable(Date.prototype.toGMTString, "name");
-verifyNotWritable(Date.prototype.toGMTString, "name");
-verifyConfigurable(Date.prototype.toGMTString, "name");

test/annexB/built-ins/Date/prototype/toGMTString/value.js

+// Copyright (C) 2016 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-date.prototype.togmtstring
+es6id: B.2.4.3
+es5id: B.2.6
+description: Value of `Date.prototype.toGMTString`
+info: >
+    The function object that is the initial value of Date.prototype.toGMTString
+    is the same function object that is the initial value of
+    Date.prototype.toUTCString.
+---*/
+
+assert.sameValue(Date.prototype.toGMTString, Date.prototype.toUTCString);