patch applied (ghc): GHCi: use non-updatable thunks for breakpoints

[Simon Marlow]

Wed Oct 10 02:32:41 PDT 2007  Simon Marlow <simonmar at microsoft.com>
  * GHCi: use non-updatable thunks for breakpoints
  The extra safe points introduced for breakpoints were previously
  compiled as normal updatable thunks, but they are guaranteed
  single-entry, so we can use non-updatable thunks here.  This restores
  the tail-call property where it was lost in some cases (although stack
  squeezing probably often recovered it), and should improve
  performance.

    M ./compiler/ghci/ByteCodeAsm.lhs +2
    M ./compiler/ghci/ByteCodeGen.lhs -2 +10
    M ./compiler/ghci/ByteCodeInstr.lhs -2 +5
    M ./includes/Bytecodes.h -26 +27
    M ./includes/StgMiscClosures.h +2
    M ./rts/Apply.cmm +70
    M ./rts/Interpreter.c -1 +12