I've renamed a number of type and data constructors within Cmm so that
the names used in the compiler may more closely reflect the C--
specification 2.1.  I've done a bit of other renaming as well.
Highlights:

  CmmFormal and CmmActual now bear a CmmKind (which for now is a
                                              MachHint as before)
  CmmFormals = [CmmFormal] and CmmActuals = [CmmActual]
  
  suitable changes have been made to both code and nonterminals in the
  Cmm parser (which is as yet untested)

  For reasons I don't understand, parts of the code generator use a
  sequence of 'formal parameters' with no C-- kinds.  For these we now
  have the types
    type CmmFormalWithoutKind   = LocalReg
    type CmmFormalsWithoutKinds = [CmmFormalWithoutKind]

  A great many appearances of (Tau, MachHint) have been simplified to
  the appropriate CmmFormal or CmmActual, though I'm sure there are
  more opportunities.

  Kind and its data constructors are now renamed to
     data GCKind = GCKindPtr | GCKindNonPtr 
  to avoid confusion with the Kind used in the type checker and with CmmKind.

Finally, in a somewhat unrelated bit (and in honor of Simon PJ, who
thought of the name), the Whalley/Davidson 'transaction limit' is now
called 'OptimizationFuel' with the net effect that there are no longer
two unrelated uses of the abbreviation 'tx'.