TextBackGround procedure

  DECLARATION:  TextBackGround(Color : Byte);

      PURPOSE:  Sets the text background color

         UNIT:  CRT

      REMARKS:  Color must be an integer expression, ranging from 0 to 7
                or you may use the constants that have been declared in
                the CRT Unit as follows:

                            Const
                               Black      =  0;
                               Blue       =  1;
                               Green      =  2;
                               Cyan       =  3;
                               Red        =  4;
                               Magenta    =  5;
                               Brown      =  6;
                               LightGray  =  7;
                               DarkGray   =  8;

                TextBackground actually sets bits 4..6 in the TextAttr
                variable, which is used to hold the current video attributes
                in the CRT Unit.