[ES6] Add Reflect namespace and add Reflect.deleteProperty

[ES6] Add Reflect namespace and add Reflect.deleteProperty
https://bugs.webkit.org/show_bug.cgi?id=147287

Reviewed by Sam Weinig.

This patch just creates the namespace for ES6 Reflect APIs.
And add template files to implement the actual code.

Not to keep the JS generated properties C array empty,
we added one small method, Reflect.deleteProperty in this patch.

* CMakeLists.txt:
* DerivedSources.make:
* JavaScriptCore.vcxproj/JavaScriptCore.vcxproj:
* JavaScriptCore.vcxproj/JavaScriptCore.vcxproj.filters:
* JavaScriptCore.xcodeproj/project.pbxproj:
* builtins/ReflectObject.js: Added.
(deleteProperty):
* runtime/CommonIdentifiers.h:
* runtime/JSGlobalObject.cpp:
(JSC::JSGlobalObject::init):
* runtime/ReflectObject.cpp: Added.
(JSC::ReflectObject::ReflectObject):
(JSC::ReflectObject::finishCreation):
(JSC::ReflectObject::getOwnPropertySlot):
* runtime/ReflectObject.h: Added.
(JSC::ReflectObject::create):
(JSC::ReflectObject::createStructure):
* tests/stress/reflect-delete-property.js: Added.
(shouldBe):
(shouldThrow):

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@187401 268f45cc-cd09-0410-ab3c-d52691b4dbfc