Allow markup and links in the info bar.
    
    This changes the behavior of
    anaconda_base_window_set_{error,info_warning}, in that the message
    parameter is now treated as markup. Encourage the use of links in the
    message in order to add something activatable to the tab order. The
    actual link URI will be ignored.
    
    Change the info-bar-clicked event to activate on button-pressed instead
    of button-released, which keeps us from both a button event and a link
    event if someone clicks on a link.