BUGFIX: System.Cmd.system was used here but the executable path may
have spaces.  The right way is to use runInteractiveProcess but it isn't
supported from HUGS.  It is easier for a while to quote the path.

That is, hooks to override basic behavior of configure, install, etc.
Basic use case for this is in over-riding the "install" behavior for
cgi-bin tools.


In addition to the existing hooks, that gives us:


     confHook :: PackageDescription -> ConfigFlags -> IO LocalBuildInfo,
     buildHook :: PackageDescription
               -> LocalBuildInfo
               -> Int                 -- verbose
               -> [ PPSuffixHandler ]
               -> IO (),
     cleanHook :: PackageDescription -> LocalBuildInfo -> Int -> [PPSuffixHandler] -> IO (),
     copyHook :: PackageDescription
              -> LocalBuildInfo
              -> (Maybe FilePath,Int) -- ^install-prefix, verbose
              -> IO (),
     instHook :: PackageDescription
              -> LocalBuildInfo
              -> Int -- verbose
              -> Bool -- user install?
              -> IO (),
     sDistHook :: FilePath -- ^build prefix (temp dir)
               -> FilePath -- ^TargetPrefix
               -> Int      -- ^verbose
               -> Bool     -- ^snapshot
               -> [PPSuffixHandler]  -- ^ extra preprocessors (includes suffixes)
               -> PackageDescription
               -> IO (),
     regHook :: PackageDescription -> LocalBuildInfo -> RegisterFlags -> IO (),
     unregHook :: PackageDescription -> LocalBuildInfo -> RegisterFlags -> IO (),
     haddockHook :: PackageDescription -> LocalBuildInfo -> Int -> [PPSuffixHandler] -> IO (),
     pfeHook :: PackageDescription -> LocalBuildInfo -> Int -> [PPSuffixHandler] -> IO ()

I don't really know if these types are good, but they are the types
needed by the "default" hooks which do the guts of the
Distribution.Simple work.  I'm not happy with the handling of
LocalBuildInfo which you can't avoid generating at this point, because
all the post-hooks need it.

  Invoke the configure program (if present) directly instead of using sh,
  except under MinGW, where #! won't work.  (Problem noted by Frederik Eaton)

  * rename other-files as extra-source-files
  
  * new field extra-tmp-files

  buildGHC: reset search path before adding hs-source-dirs, so that these
  are the only directories GHC searches.

  installHugs: quote the script name to protect spaces, and create .bat
  files for executables under Windows.

Always invoke the ld.exe that is in $ghc-bin\..\gcc-lib on Windows, because ld is probably not in the path on Windows.

  tweak SHGetFolderPath
  preprocess: Hugs+MinGW: remove special case
  test *_HOST_OS (as well as *_TARGET_OS, which is there for old GHC's)
  take care of string literals while stripping comments
  rearrange so that we print "Compiling FFI stubs" at most once
  only run ffihugs on Main module if required
  add comment about older Windows versions
  Hugs only: avoid SHGetFolderPath for now
  convert input file paths to platform form (from Brian Smith)
  convert paths to native form at entry
  rename --builddir as --scratchdir to avoid clash with autoconf --build flag.

  doc: consolidate descriptions of preprocessors

tweak to Configure for windows. removed DefaultSetup since it breaks windows cabal 1.0 installations.