tw_ScrDel( scrpos, scr1, leng, wid )
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     Delete a screen line from a Clipper SAVESCREEN() variable.

       Arguments:

     scrpos - 'C' "T", "L", "B", "R" for: top, left, bottom or right of
                   the present screen.

     scr1   - ''  Screen to delete from.

     leng   - ''  Length of screen.

     wid    - ''  Width of screen.

       Return:

     Clipper SAVESCREEN() variable.

       Example:

     WHIDDEN := tw_ScrDel( "B", WHIDDEN, SLENGTH, SWIDTH + 1 )