Known bugs

html, all:
        - keys can move the vertical scrollbar, but the window moveth not.
        problem in wxHTML.

        - widgets are not removed when the HTML contents is changed
        (this can be fixed by adding ~HtmlWidgetCell { wnd->Destroy(); } )

        - potential problem with the use of ThreadState in html.i
        (mainly because I don't really know what I'm doing there)

html, msw:
        - vertical scrollbar behaves erratically when content smaller than
        window

        - page with widgets takes forever to draw when constructed
        in frame constructor

        - sometimes the python scripts with html crash on startup, before
        the window is displayed (illegal operation). this seems mainly to
        happen when the various libs are not yet in the disk cache. race
        condition?