Draws a wall on screen. For Floyd fans only! <g>
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 Syntax

        GT_TheWall([<nTop>],[<nLeft>],[<nBottom>],[<nRight>],;
                   [<cColour>]) --> NIL

 Arguments:

      <nTop>, <nLeft>, <nBottom> and <nRight> are the screen co-ordinates
      at which to draw the wall. The defaults are 0, 0, maxrow(), maxcol().

      <cColour> is an optional string parameter that is the colour if the
      wall. If not supplied this defaults to the current colour.

 Returns:

      Nothing.

 Description:

      GT_TheWall() draws a wall on your screen. It could be nice as a
      background for your applications.

 Examples:

      // Draw a wall on the screen fitting inside a border.

      dispbox(0,0,maxrow(),maxcol(),"w+/b")
      GT_TheWall(1,1,maxrow()-1,maxcol()-1,"w/r")

 Source: THEWALL.PRG

 Author:  Dave Pearson