Got racket/stream to compile for new generics setup.

There is no need for gen:stream to use define-generics.  It can simply use
define-syntax and make-generic info, like gen:equal+hash and gen:custom-write.
This removes the burden of using local names for the methods and using
stream-ref from racket/private/for.
Fixed import of racket/private/generic in racket/generic.
All of the racket collection compiles now.
Updated use of racket/private/generic in data/order.