patch applied (cabal): Allow $arch and $os in install paths.

[Duncan Coutts]

Tue Jul 29 08:19:52 PDT 2008  Duncan Coutts <duncan at haskell.org>
  * Allow $arch and $os in install paths.
  Fixes ticket #312. For example a user could use:
    cabal configure --libsubdir="$pkgid/$compiler/$arch"
  if they wanted to have packages for multiple architectures
  co-exist in the same filestore area.

    M ./Distribution/Simple/InstallDirs.hs -2 +11

View patch online:
http://darcs.haskell.org/cabal/_darcs/patches/20080729151952-adfee-15065b6381988d9baeb53345bde01f42b0c4f45f.gz