+ 2001/03/29 vers 1.02
Changes from Raphael Manfredi <Raphael_Manfredi@pobox.com> to
add serialize method callbacks using Storable.
In addition Callback now dies if a method for a method callback
does not exist at the time of creation.
+ 2000/08/22 vers 1.02
Changes from Raphael Manfredi <Raphael.Manfredi@st.com> to
add the method form of callback invocation.