Sat May 6 13:01:34 EST 2006 Don Stewart <dons@cse.unsw.edu.au>

Sat May  6 13:01:34 EST 2006  Don Stewart <dons@cse.unsw.edu.au>
  * Do loopU realloc on the Haskell heap. And add a really tough stress test

Sat May  6 12:28:58 EST 2006  Don Stewart <dons@cse.unsw.edu.au>
  * Use simple, 3x faster concat. Plus QC properties. Suggested by sjanssen and dcoutts

Sat May  6 15:59:31 EST 2006  Don Stewart <dons@cse.unsw.edu.au>
  * dcoutt's packByte bug squashed

  With inlinePerformIO, ghc head was compiling:

   packByte 255 `compare` packByte 127

  into roughly

   case mallocByteString 2 of
       ForeignPtr f internals ->
            case writeWord8OffAddr# f 0 255 of _ ->
            case writeWord8OffAddr# f 0 127 of _ ->
            case eqAddr# f f of
                   False -> case compare (GHC.Prim.plusAddr# f 0)
                                         (GHC.Prim.plusAddr# f 0)

  which is rather stunning. unsafePerformIO seems to prevent whatever
  magic inlining was leading to this. Only affected the head.