* Make Any into a type family (which it should always have been)
  This is to support the future introduction of eta rules for
  product types (see email on ghc-users title "PolyKind issue"
  early Sept 2012)

* Add the *internal* data type support for
    (a) closed type families [so that you can't give
        type instance for 'Any']
    (b) injective type families [because Any is really
        injective]
  This amounts to two boolean flags on the SynFamilyTyCon
  constructor of TyCon.SynTyConRhs.

There is some knock-on effect, but all of a routine nature.

It remains to offer source syntax for either closed or
injective families.