These changes were causing build failures and assertion failures on
        Windows.

JavaScriptCore:

        * JavaScriptCore.vcproj/JavaScriptCore/JavaScriptCore.def:
        * JavaScriptCore.vcproj/JavaScriptCore/JavaScriptCore_debug.def:
        * JavaScriptCore.xcodeproj/project.pbxproj:
        * runtime/JSArray.cpp:
        * runtime/StringPrototype.cpp:
        * runtime/UString.cpp:
        * runtime/UString.h:
        * wtf/FastMalloc.cpp:
        * wtf/FastMalloc.h:
        * wtf/Platform.h:
        * wtf/PossiblyNull.h: Removed.

WebCore:

        * ForwardingHeaders/wtf/PossiblyNull.h: Removed.
        * platform/graphics/cg/ImageBufferCG.cpp:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@46180 268f45cc-cd09-0410-ab3c-d52691b4dbfc