This implements kind equalities, according to the "System FC with
Explicit Kind Equalities" paper.
See https://ghc.haskell.org/trac/ghc/wiki/DependentHaskell/Phase1 for
details. This branch is available at github.com/goldfirere/ghc,
on the nokinds branch.
The initial diff is still very much a work in progress; there are
181 failures in the testsuite. A good deal of these have known causes,
and an unknown number are simple error message wibbles. (I haven't
had a chance to go through all the errors yet.)