cabal: configure --user imples install --user

[Isaac Jones]

I am changing the behavior of user vs global installations slightly,
and I'm wondering if anyone sees a problem with this.  It seems to
make much more sense than what we were doing.  Commit log follows.

peace :)

  isaac


  Modified files:
    libraries/Cabal/Distribution Setup.hs Simple.hs 
    libraries/Cabal/Distribution/Compat FilePath.hs 
    libraries/Cabal/Distribution/Simple Configure.hs 
                                        LocalBuildInfo.hs 
  Log:
  modified install --user behavior to include configure --user
  
  If the user configures with --user, that means that they are willing
  to satisfy dependencies from the user databaes.  If that's the case,
  then it really only makes sense to install the package as --user as
  well, since if user A installs configures / builds the package with
  --user, then installs it as root, user B may attempt to use the
  package and not be able to fulfill the dependencies.  Therefore, if
  the package is configured as --user, then we also will call ghc-pkg
  with --user.
  
  Of course, in this case:
  
  ./setup configure --user
  ./setup install --global
  
  Cabal will accept the user's instructions to install this globally,
  however ill conceived.  This changes the type of the install hook,
  btw, since we now need to be able to tell the difference between
  passing the --global flag and not passing any flag.
  
  Any objections to this change?