In contrast to AbsorbingPolynomial, the parser of Polynomial was written
polymorphic in the monad, which can cost quite some performance. We now
specialize to the concrete monad.

Polynomials are now only transformed to AbsorbingPolynomials if their functor
expression has actual inner functors. Otherwise it's not necessary to save
intermediate states and we don't have to pay the performance penalty of
AbsorbingPolynomial's more complicated refinement interface.

AbsorbingPolynomial can now wrap any type that implements the refinement
interface, not just SomeFunctor

This helps GHC realize that it really should specialize the refineWithStats
function for the specific type of its argument.

This facilitats specializing the algorithm for specific functors.

This reverts commit f8b942f4 partially

This means that "Xfoo" won't parse, but "X" will. Previously, non-parsable
suffixes had been ignored.

There was a revision of the json packages on hackage that changed the
constraints on base, leading to it not building any more for me. This flag
change fixes it.

See also http://hackage.haskell.org/package/json-0.9.3/revisions/

This warning is really annoying.