Re-add FunTy (big patch)

With TypeInType Richard combined ForAllTy and FunTy, but that was often
awkward, and yielded little benefit becuase in practice the two were
always treated separately.  This patch re-introduces FunTy.  Specfically

* New type
    data TyVarBinder = TvBndr TyVar VisibilityFlag
  This /always/ has a TyVar it.  In many places that's just what
  what we want, so there are /lots/ of TyBinder -> TyVarBinder changes

* TyBinder still exists:
    data TyBinder = Named TyVarBinder | Anon Type

* data Type = ForAllTy TyVarBinder Type
            | FunTy Type Type
            |  ....

There are a LOT of knock-on changes, but they are all routine.

The Haddock submodule needs to be updated too

1 files changed, 0 insertions, 0 deletions

diff --git a/libraries/time b/libraries/time
-Subproject 52e0f5e85ffbaab77b155d48720fb216021c8a7
+Subproject a73564c366b15f7057b614188662d7b7a8eaab1