Reviewed by Nikolas Zimmermann.

        Bug 22858: Simplify make_names.pl code for avoiding multiple definitions or inclusions
        https://bugs.webkit.org/show_bug.cgi?id=22858

        I had introduced an awkward situation using hasCustomJSWrapper and
        sometimes boolean parameter in order to ensure JS wrapper generated once
        or header included once.

        Simplified the code by using a %seenTag hash to detect multiple definitions
        or inclusions and skipping it.

        Also cleaned up a bit make_names.pl by using more explicit names and moving
        code to where it belongs.

        * dom/make_names.pl:
        * html/HTMLTagNames.in: Necessary changes that were not detected by
        the previous syntax but will be required for autogenerating HTMLElementFactory.




git-svn-id: http://svn.webkit.org/repository/webkit/trunk@39666 268f45cc-cd09-0410-ab3c-d52691b4dbfc