- added primops for read&writing StablePtrs to ByteArrays, Adds and FOs
- egcs crashes in odd ways when encountering the typedefs we need to
  produce when compiling 'foreign import dynamic's. To workaround the
  problem, kludgily add a CCallTypedef constructor to AbsCSyn.AbstractC
  which the flattener will produce (at the toplevel) when encountering
  CCallOps inside COptStmts.
- augmented PrimOp.CCallOp to carry a unique when it represents a
  'foreign import dynamic' call. The CoreToStg pass ensures that these
  uniques are exactly that. They're used to eventuall generate (unique)
  typedef names.