patch applied (cabal-install): After refactoring the http proxy code we don't need the unix package

[Duncan Coutts]

Mon Jan 14 06:23:01 PST 2008  Duncan Coutts <duncan at haskell.org>
  * After refactoring the http proxy code we don't need the unix package
  Which was just being used for an exception-free version of getEnv but we
  have to cope with exceptions anyway for the Win32 registry.

    M ./cabal-install.cabal -2