patch applied (cabal): Prefix the datadir env var with the package name

[Duncan Coutts]

Wed May 14 02:42:03 PDT 2008  Duncan Coutts <duncan at haskell.org>
  * Prefix the datadir env var with the package name
  Partly as it is more likely not to clash with other users and since
  in general different libs within a program may need different paths.

    M ./Distribution/Simple/Build.hs -7 +8

View patch online:
http://darcs.haskell.org/cabal/_darcs/patches/20080514094203-adfee-ca47239e157a29a7d7232f017c9cd78332633818.gz