make b* binders for defprod/defaggregate extensible
VL: Split representation of ports into interface/noninterface cases.  Adjusted sizing to skip interface ports.  Added interface ports to scopestacks.  Adjusted all the other transforms to deal with the change.
Add more advanced default hints for std::define returnspecs and deffixequiv(-mutual) forms.
merge
Define/defines/deffixequiv: Improved default hint setup for inductive
proofs.  VL: settled some problems with contexts and the splitting of
regular/interface ports.
merge
(Merge): VL: Split port representation into two types for regular and
interface ports; add mechanism for setting up default hints for
define/defines returnspec proofs and deffixequiv proofs, and add some
good default settings for these hints.