WebCore portion of multipart/x-mixed-replace support

        * khtml/misc/loader.cpp:
        (Request::Request):
        (Loader::slotReceivedResponse):
        Only allow a multipart load for images, clear out the old multipart section to prepare for a replace
        (Loader::slotData):
        Multipart sections are delivered to the coreLoader by WebKit all at once, send eof to CachedImage::data
        * khtml/misc/loader.h:
        (khtml::CachedObject::isImage): Added
        (khtml::CachedImage::isImage):
        * kwq/KWQKJobClasses.h:
        * kwq/KWQKJobClasses.mm:
        (KIO::TransferJob::cancel):
        Added a way to cancel a subresource loader from WebCore
        * kwq/KWQLoader.h:
        * kwq/KWQLoader.mm:
        (KWQResponseIsMultipart):
        * kwq/KWQResourceLoader.h:
        * kwq/KWQResourceLoader.mm:
        (-[KWQResourceLoader jobCanceledLoad]):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@10490 268f45cc-cd09-0410-ab3c-d52691b4dbfc