patch applied (packages/base): Disable unpack/build fusion

[Don Stewart]

Sun Jul  2 01:39:13 PDT 2006  Don Stewart <dons at cse.unsw.edu.au>
  * Disable unpack/build fusion
  
  unpack/build on bytestrings seems to trigger a bug when interacting with
  head/build fusion in GHC.List. The bytestring001 testcase catches it.
  
  I'll investigate further, but best to disable this for now (its not
  often used anyway).
  
  Note that with -frules-off or ghc 6.4.2 things are fine. It seems to
  have emerged with the recent rules changes.
  

    M ./Data/ByteString.hs -14 +10