Language enhancements

[Michael Latta]

I am considering creating a VM for Self with some language extensions 
and would like comments:

1) I am considering making the inheritance of structural slots 
declarative.  Rather than listing the copydowns in each child object, 
allowing the parent to annotate a slot as copied.  The child objects 
would still need to be able to exclude those they replace with 
behavior.

2) I am considering adding an annotation to a slot that will cause it 
to be cloned when the object is cloned.

These ideas come from working with modeling where there is more 
declarative work.  The items above would also need syntax to support 
textual definition of those aspects.  For example 2 above could be 
<slot>+ to indicate aggregation.  The idea is to reduce errors and 
reduce code to manage these aspects of a system.

Let me know what you think, or if there are good reasons to leave it in 
code.

Michael