type-equality-1: Data.Type.Equality compat package

This library defines a propositional equality data type, shims Data.Type.Equality as well as possible for older GHCs (< 7.8).

data a :~: b where
    Refl :: a :~: a

The module Data.Type.Equality.Hetero shims :~~: equality, for compilers with PolyKinds