[XBL] Editorial: diagram in section 3.7

It would be nice if the diagram in section 3.7 would contain labels
pointing to the base binding,  base bindings of the chain, and most
derived binding. Or make an additional diagram that shows the bindings
in a linear chain with the labels for each kind of binding, as well as
illustrating explicit and implicit inheritance. Either would be good in
more clearly illustrating how inheritance works in XBL and how to use
the above terminology. 

Marcos