This fixes at least one "potential" bug in the file
`collects/pkg/private/create.rkt`, where `else` in the
`cond` is bound to `else` from `match` instead of `racket/base`.
(though it turns out that the format will always be
truthy, making the program happen to be correct.)
This commit merges changes that were developed in the "racket7" repo.
See that repo (which is no longer modified) for a more fine-grained
change history.
The commit includes experimental support for running Racket on Chez
Scheme, but that "CS" variant is not built by default.
