Reviewed by Maciej.

    Reviewed by Maciej.

        - fixed <rdar://problem/3744583> Safari can not quit when a webpage has a login sheet
        that can't be cancelled.

        The proper fix for this would be to change the class of the NSPanel in the nib file.
        But since this would require a localization change, I did a run-time hack instead.
        I'll file a bug about fixing this when we're out of localization freeze.

        * Panels.subproj/WebAuthenticationPanel.m:
        (-[WebAuthenticationPanel replacePanelWithSubclassHack]):
        new method, creates a new panel that is identical to the original one except that
        it's our subclass, and moves all the subviews of the original panel into the new one.
        (-[WebAuthenticationPanel loadNib]):
        call replacePanelWithSubclassHack
        (-[NonBlockingPanel _blocksActionWhenModal:]):
        only method of new NSPanel subclass; overrides this SPI to allow the user to quit
        when one of these panels/sheets is on-screen

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@8199 268f45cc-cd09-0410-ab3c-d52691b4dbfc