set_window_strut function

Proposing a `set_window_strut` function which sets ```_NET_WM_STRUT_PARTIAL``` property which reserves space at the edge of the screen. E.g. I can write

    if (get_application_name() == "Conky (desktop)") then
        set_window_size(1916, 16)
        set_window_strut(0, 0, 16, 0, 0, 0, 0, 0, 1920, 3840)
    end

    if (get_application_name() == "Pidgin" and get_window_role() == "conversation") then
        undecorate_window()
        set_skip_pager(true)
        set_skip_tasklist(true)
        set_window_geometry(1920 * 2 - 640, 600, 640, 480)
        set_window_strut(0, 640, 0, 0, 0, 0, 600, 1080, 0, 0, 0, 0)
    end

Conky acts like a panel and maximized windows do not overlap pidgin conversation window (screenshot: http://storage.thelogin.ru/screenshots/2013-11-20_03:40:36.png)