Simplify genprimops

Currently, primops.txt.pp contains names of primitive types in Haskell:

primtype State# s

If this file also tracked the GHC name (e.g. primtype statePrimTyCon State# a), we could automatically generate exposedPrimTyCons and remove special cases in genprimopcode such as

ppType (TyApp (TyCon "State#") [x])             = "mkStatePrimTy " ++ ppType x

We already track the internal name for primops.