+ 2002/11/20 vers 1.04

Can now create callback objects from callback objects.

Fix t/store.t -- it appears that the old require syntax for
specific versions no longer works.

+ 2001/03/29 vers 1.02 & 1.03

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.