This allows us to remove forward declarations for these classes from
WebCore/WebKit (a step in moving these class from WebCore:: to WTF::).

Rubber stamped by Sam Weinig

JavaScriptCore: 

* JavaScriptCore.xcodeproj/project.pbxproj:
* wtf/Forward.h:

WebCore: 

* WebCore.xcodeproj/project.pbxproj:
* accessibility/AXObjectCache.h:
* accessibility/AccessibilityARIAGrid.h:
* accessibility/AccessibilityListBoxOption.h:
* accessibility/AccessibilityObject.h:
* accessibility/AccessibilityRenderObject.h:
* accessibility/AccessibilityTable.h:
* bindings/cpp/WebDOMCString.h:
* bindings/cpp/WebDOMString.h:
* bindings/gobject/ConvertToUTF8String.h:
* bindings/js/DOMWrapperWorld.h:
* bindings/js/JSDOMBinding.h:
* bindings/js/JSDOMWindowBase.h:
* bindings/js/JSMessagePortCustom.h:
* bindings/js/JavaScriptCallFrame.h:
* bindings/js/ScriptController.h:
* bindings/js/ScriptProfile.h:
* bindings/js/ScriptSourceProvider.h:
* bindings/js/ScriptString.h:
* bindings/js/WorkerScriptC...