Possibly replace Constraints module with library

The type unification in Constraints.hs is a little messy and could probably just be replaced with an existing (hopefully very fast!) unification library. Does anyone know what the state-of-the-art is in the Haskell world? (I haven't used any before...)

Start by reading Constraints.hs to understand the current type-unification implementation and its interfaces. Research existing Haskell unification libraries and compare their suitability and performance for Carp; done would be a documented library recommendation and an agreed replacement scope.

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