Made a DOMNode category in DOMEvents.h that lets DOMNode conform to the
        DOMEventTarget protocol that works with GCC 5412.

        Removed forward declarations of WebCoreWidgetHolder and imported WebCoreWidgetHolder.h.

        Removed all <Cocoa/Cocoa.h> and <Foundation/Foundation.h> imports in other headers,
        we import <Cocoa/Cocoa.h> in the prefix header for ObjC.

        * WebCore.xcodeproj/project.pbxproj:
        * bindings/objc/DOMCore.h:
        * bindings/objc/DOMEvents.h:
        * bridge/mac/FormDataMac.h:
        * bridge/mac/WebCoreAXObject.h:
        * bridge/mac/WebCoreCache.h:
        * bridge/mac/WebCoreEncodings.h:
        * bridge/mac/WebCoreFrameBridge.h:
        * bridge/mac/WebCoreFrameNamespaces.h:
        * bridge/mac/WebCoreJavaScript.h:
        * bridge/mac/WebCorePageBridge.h:
        * bridge/mac/WebCorePageState.h:
        * bridge/mac/WebCoreResourceLoader.h:
        * bridge/mac/WebCoreScriptDebugger.h:
        * bridge/mac/WebCoreSettings.h:
        * bridge/mac/WebCoreStringTruncator.h:
        * bridge/mac/WebCoreStringTruncator.mm:
        * bridge/mac/WebCoreTextDecoder.h:
        * bridge/mac/WebDashboardRegion.h:
        * kcanvas/device/quartz/KRenderingDeviceQuartz.mm:
        * platform/mac/CookieJar.mm:
        * platform/mac/DeprecatedStringMac.mm:
        * platform/mac/FontDataMac.mm:
        * platform/mac/FoundationExtras.h:
        * platform/mac/TextBoundaries.mm:
        * platform/mac/WebCoreHistory.h:
        * platform/mac/WebCoreHistory.m:
        * platform/mac/WebCoreKeyGenerator.h:
        * platform/mac/WebCoreTextArea.h:
        * platform/mac/WebCoreTextField.h:
        * platform/mac/WebCoreTextRenderer.h:
        * platform/mac/WebCoreView.h:
        * platform/mac/WebCoreWidgetHolder.h:



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@15438 268f45cc-cd09-0410-ab3c-d52691b4dbfc