checkpoint revision of type relations in rel.fs
sketching slack system
refining slack system
midstream check in ... more progress on rel.fs
rel.fs is code complete
moving towards restoring compilation
everything compiles again
new implementation of type relations in rel2.fs (deferred constraints, slack, etc.); the functionality is still disabled. The old implementation is in rel1.fs and is still the active one. will migrate to rel2 and remove rel1.fs eventually