darcs patch: Added GZipUtils to handle .tar files wit... (and 1 more)

2 patches for repository http://darcs.haskell.org/cabal-install: Tue Oct 26 23:23:43 EEST 2010 Dmitry Astapov <dastapov@gmail.com> * Added GZipUtils to handle .tar files with the same code as .tar.gz Wed Oct 27 00:26:06 EEST 2010 Dmitry Astapov <dastapov@gmail.com> * Use "maybeDecompress" to handle broken proxies that transparenty decompress network streams. Closes #622, #686. Cabal update could fail in some cases, see http://trac.haskell.org/http/ticket/109283