patch applied (cabal): Pattern match on an OS datatype rather than using ifdef everywhere

[Ian Lynagh]

Sun Aug  5 06:03:47 PDT 2007  Ian Lynagh <igloo at earth.li>
  * Pattern match on an OS datatype rather than using ifdef everywhere

    M ./Cabal.cabal +1
    M ./Distribution/Program.hs -5 +6
    M ./Distribution/Simple/Build.hs -15 +15
    M ./Distribution/Simple/Configure.hs -20 +9
    M ./Distribution/Simple/GHC.hs -22 +16
    M ./Distribution/Simple/Hugs.hs -11 +13
    M ./Distribution/Simple/LocalBuildInfo.hs -32 +16
    M ./Distribution/Simple/Register.hs -49 +40
    M ./Distribution/Simple/Utils.hs -11 +7
    A ./Distribution/System.hs