Display a boxed window on the screen.
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 Syntax

        GT_Window(<nTop>,<nLeft>,<nBottom>,<nRight>, ;
            [<cLines>],[<cColour>],[<cTitle>],[<lShadow>]) ;
            => lSuccess

 Arguments:

      <nTop>],[<nLeft>],[<nBottom>,<nRight>] are the
      corners of the box.

      <cColour> is an optional colour string.

      <cBoxLines> are the optional box lines to use.

      <cTitle> is the optional title.

      <lShadow> shadow the box ?

 Returns:

      .T. / .F. based on the success.

 Description:

      Display a boxed window on the screen.

 Examples:

      // Window, default colours, lines and shadow and no
      // title
      GT_Window(05,10,15,20)

 Source: GT_WINDO.PRG

 Author:  Martin Bryant