use clipping in the recent commit to actually test bounding boxes
added a void contract to fix setup
Cleanup kw/opt lambda annotations.
Make kw/opt lambda special checks work with other expected values.

Closes PR13544.
Reduce unnecessarily complicated restrict case.
Fix type of split-at and vector-split-at.

Closes PR12700.
tidy up gui

Also improve the speed of compute-diffs by approximately 350x
(from 18+ seconds to about 50 milliseconds on the test case
that's currently failing)
make-traversal's optional argument is now ignored

Recent changes eliminated it, but it seems better
(for backwards compatibility) to leave it there but
ignore it
Redex: generation for judgment-form side-conditions

- enable generation for the above by compiling to
a disequation with "#f"

- wrap bare terms in relation definitons in
  side-conditions (require they not be "#f")