Reviewed by Oliver Hunt.

        Made JSWrapperObject and subclasses moving-GC-safe
        https://bugs.webkit.org/show_bug.cgi?id=56346
        
        SunSpider reports no change.

        * runtime/BooleanObject.cpp:
        (JSC::BooleanObject::BooleanObject):
        * runtime/DateInstance.cpp:
        (JSC::DateInstance::DateInstance): No more need for JSGlobalData, since
        we don't initialize the wrapped value in our constructor.

        * runtime/DateInstance.h: Don't set the OverridesMarkChildren flag because
        we do not in fact override markChildren.

        * runtime/DatePrototype.h: Declare an anonymous slot, since wrapper object
        no longer does so for us. Also added an ASSERT to catch a latent bug,
        where DatePrototype stomped on its base class's anonymous slot. Hard-coded
        anonymous slots are a plague on our code. This doesn't cause any problems
        in our existing code since the base class never reads the anonymous slot
        it declares, but it caused crashes when I tried to start using the slot
        in an initial version of this patch.

        * runtime/JSWrapperObject.h:
        (JSC::JSWrapperObject::JSWrapperObject):
        (JSC::JSWrapperObject::internalValue):
        (JSC::JSWrapperObject::setInternalValue): Resolved a problem where
        our internal value was stored in two places: an anonymous slot, and a
        data member which was not always visited during GC. Now, we only use the
        data member, and we always visit it. (Instead of relying on certain
        subclasses to set the OverridesMarkChildren bit, we set it ourselves.)

        * runtime/NumberObject.cpp:
        (JSC::NumberObject::NumberObject): No more need for JSGlobalData, since
        we don't initialize the wrapped value in our constructor.

        * runtime/NumberObject.h: Removed meaningless declaration.

        * runtime/StringObject.cpp:
        (JSC::StringObject::StringObject): No more need for JSGlobalData, since
        we don't initialize the wrapped value in our constructor.

        * runtime/StringObject.h: Don't set the OverridesMarkChildren flag because
        we do not in fact override markChildren.

        * runtime/StringPrototype.h: Declare an anonymous slot, since wrapper object
        no longer does so for us. Also added an ASSERT to catch a latent bug,
        where DatePrototype stomped on its base class's anonymous slot. Hard-coded
        anonymous slots are a plague on our code.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@81086 268f45cc-cd09-0410-ab3c-d52691b4dbfc