Since a CmmCall returns CmmFormals which may include
global registers (and indeed one place in the code
returns the results of a CmmCall into BaseReg) and
since CPS conversion will change those return slots
into formal arguments for the continuation of the call,
CmmProc has to have CmmFormals for the formal arguments.

Oddly, the old code never made use of procedure arguments
so this change only effects the types and not any of the code.
(Because [] is both of type [LocalReg] and CmmFormals.)

The function
  listSplitUniqSupply :: UniqSupply -> [UniqSupply]
splits a UniqSupply into an infinite list of supplies.
It is a generalization of splitUniqSupply.

This is a safety check-in, before I begin a cleanup.

At present it just annotates each block with a comment
indicating what local registers are live at the start
of the block.

Dataflow.hs contains an early draft of the live variable analysis.
This draft contains known bugs and is being recorded only to provide
a point to be revert back to if necessary.

See Note [Recursive rules] in OccurAnal

Fans of the banner can add
    putStrLn "   ___         ___ _"
    putStrLn "  / _ \\ /\\  /\\/ __(_)"
    putStrLn " / /_\\// /_/ / /  | |   GHC Interactive, for Haskell 98."
    putStrLn "/ /_\\\\/ __  / /___| |   http://www.haskell.org/ghc/"
    putStrLn "\\____/\\/ /_/\\____/|_|   Type :? for help."
    putStrLn ""
to their ~/.ghci

The logic for printing the ghc and ghci usage messages was inverted.
However, the ghci case will never actually happen with the current code,
as we print a usage message when cli_mode == ShowUsage and choose the
ghci usage message if cli_mode == DoInteractive. This should be fixed
as part of a larger options handling overhaul.

See Note [Closure conversion] in OccurAnal for details of this
patch (which merely involves *deleting* a test!).  The test case
was produced by Roman, and shows up when doing closure conversion
and vectorisation for data parallelism.  But perhaps other times too.

There was a rather subtle bug in the way 'oclose' works when
generalising top-level function definitions.  See
	Note [Important subtlety in oclose]
in FunDeps for an explanatoin.

I also tidied up duplication in comments while I was here.

This improvement arose from a suggestion in Trac #1465