def column_width colindex, width
      @cw[colindex] ||= width
      if @chash[colindex].nil?
        @chash[colindex] = ColumnInfo.new("", width) 
      else
        @chash[colindex].w = width
      end
      @chash
    end
def column_width colindex, width
      @cw[colindex] ||= width
      if @chash[colindex].nil?
        @chash[colindex] = ColumnInfo.new("", width) 
      else
        @chash[colindex].w = width
      end
      @chash
    end
set width of a given column
 @param [Number] column offset, starting 0
 @param [Number] width