[racket-dev] struct + match not interacting via a macro

I'm afraid omit-defined-values didn't work.  I'm not entirely sure how
to carry through Jay's proposal, and I also need something that will
work inside the local context of ASL (which imposes some
restrictions).  Joe Politz suggested I just go with SET! instead --
roughly,

-->
(begin
  (define-struct ...)
  (set! ...))

which can be made to work in a local context --

-->
(begin
  (define-struct ...)
  (set! dummy ...))

and so on, but now local is trying to parse the define-struct, and
doesn't like #:mutable, and removing that means that the name of the
mutator appears to Racket to be unbound because of hygiene.  Let's see
what else I can do!

Shriram