Reviewed by Maciej.

    Reviewed by Maciej.

        - re-fixed <rdar://problem/3760910> please add support for custom tag names in HTML

        * khtml/xml/dom_docimpl.cpp:
        (DocumentImpl::tagId): Use ID_LAST_TAG + 1 for the ID of the first assigned tag ID. Before we'd use ID_LAST_TAG,
        which resulted in the same number being used for ID_COMMENT and the first custom tag.
        (DocumentImpl::tagName): Use ID_LAST_TAG + 1, as above.
        (DocumentImpl::namespaceURI): Change a < ID_LAST_TAG to <= ID_LAST_TAG in the same spirit as above.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@8531 268f45cc-cd09-0410-ab3c-d52691b4dbfc