patch applied (ghc): Removed 'allow_header_set' argument from 'pack_continuation'.

[Michael Adams]

Sun Jul 15 13:22:35 PDT 2007  Michael D. Adams <adamsmd at cs.indiana.edu>
  * Removed 'allow_header_set' argument from 'pack_continuation'.
  Because branches might now go to continuations and become calls to 
  continuations, 'allow_header_set' isn't always correct.
  Removing that parameter makes the conservative approximation.
  A better approximation might save one memory store is some cases.

    M ./compiler/cmm/CmmCPSGen.hs -12 +6