Error window

        Entry:
          AX = 101Fh
          BX = bit fields
               Bits 0-12: number of characters to display
               Bits 13,14: which mouse button may be pressed to remove window
                           00 = either
                           01 = left
                           10 = right
                           11 = either
               Bit 15: beep if 1
          DS:DI -> text of message
          CH = width of error window (0 = default)
          CL = height of error window (0 = default)
          DX = segment of object handle

        Return:
          BX = status: 1 = left button, 2 = right, 27 = ESC pressed

        Note:   Window remains on-screen until ESC or indicated mouse
                button is pressed