patch applied (packages/unix): Add bindings for setting effective user-id and group-id

[Simon Marlow]

Mon May 17 11:19:45 PDT 2010  Eric Mertens <emertens at galois.com>
  * Add bindings for setting effective user-id and group-id
  
  Having the ability to set the effective user-id and group-id
  enables the application to switch between the real user-id
  and set-user-id multiple times.

    M ./System/Posix/User.hsc +33

View patch online:
http://darcs.haskell.org/cgi-bin/darcsweb.cgi?r=packages/unix;a=darcs_commitdiff;h=20100517181945-b49f3-49a874c263d9a85eaf4d45f5b41722e26fdb9771.gz