pageUp() --> self

        Repositions the data source upward and refills the display.  If the
        data source is already at logical beginning of file (i.e., the
        topmost available record is already shown), the browse cursor is
        simply moved to the top data row.  If the data source is already at
        logical beginning of file and the browse cursor is already on the
        first data row, TBrowse:hitTop is set true (.T.).