wrapped in new testing macro
added a watcher thread to check on animated gif creation
fix typo, Closes PR14720
Add edge-width option to tree-layout
Fix last commit for hv-alternating algorithm
fix module-code caching

Fixes a problem with c4508ad0d9, which disabled module-code
caching too often. A symptom of the disabled cache was that
running "math/scribblings/math.scrbl" would use twice
as much memory.
Fix PR14692
Revert "Fix PR14692"

This reverts commit 92d5408aa87043916644ec68d05b18cee2d21f69, because
it breaks the build due to recursive deps. (It also breaks if the core
is in the "racket" package.)