patch applied (ghc): Give more informative error messages

[Ian Lynagh]

Sat Nov 28 19:10:29 PST 2009  Ian Lynagh <igloo at earth.li>
  * Give more informative error messages
  We used to just get
      ghc: panic! (the 'impossible' happened)
        (GHC version 6.13.20091128 for x86_64-unknown-linux):
          too few bytes. Failed reading at byte position 32753
  with no indication of what was being parsed.

    M ./libraries/bin-package-db/Distribution/InstalledPackageInfo/Binary.hs -1 +16
    M ./libraries/bin-package-db/bin-package-db.cabal -2 +12

View patch online:
http://darcs.haskell.org/ghc/_darcs/patches/20091129031029-3fd76-35af304ce6604c1d23afdad0a035d5f8c5851bd5.gz