Procedure Init

    This procedure must be called before all other button procedures.

    The Total  variable  is  initialised  to  0.   You  may read how many
    buttons have been  created  (and  are  still  active)  in  Total, but
    never write to Total.

    Every  button  is  allocated  a   name,   picture,  number,  position
    (screen),  position  (in  linked  list),  a  key  press,  a thickness
    and a background colour.

    It is allocated some  number  which  should  be  used to identify the
    button.  It is also allocated a  position  number.   The problem with
    using linked list position  numbers  is  that if you delete the first
    button, button  position  2  becomes  position  1.   However,  if you
    use the allocated number,  when  a  button  is deleted, all the other
    buttons' numbers remain the same.