- fixed 3132382 -- crash in khtml::CachedImage

	The source of this bug was my long-ago fix to bug 3079499.
	I changed the code to copy the clients list. But this doesn't work if
	one of the clients is removed while iterating because it's deleted.
	So I made a new class, CachedObjectClientWalker, that does the iterating safely.
	Now both this new bug and the original are fixed.

        * khtml/misc/loader.cpp:
        (CachedCSSStyleSheet::checkNotify): Use CachedObjectClientWalker to walk the list.
        (CachedScript::checkNotify): Ditto.
        (CachedImage::do_notify): Ditto.
        (CachedImage::movieStatus): Ditto.
        (CachedImage::checkNotify): Ditto.
        (CachedObjectClientWalker::next): Walk the list using a list iterator, which is
	safe against the current item being removed. But go that safety one better by making
	sure you don't miss the item after one that's removed.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@3155 268f45cc-cd09-0410-ab3c-d52691b4dbfc