patch applied (cabal): Make all command line flags and flag collection types monoids

[Duncan Coutts]

Sat Dec 15 11:36:50 PST 2007  Duncan Coutts <duncan at haskell.org>
  * Make all command line flags and flag collection types monoids
  And specify command flags in a way that allows converting from or two strings.
  So not only can we parse command lines into the various flag types, we can
  convert back. This is crucial in cabal-install so that we can call Setup.hs
  scripts with all the various args, and override certain flags in a typed way
  rather than just representing them all as strings.

    M ./Distribution/Make.hs -15 +16
    M ./Distribution/Simple.hs -45 +43
    M ./Distribution/Simple/Build.hs -6 +6
    M ./Distribution/Simple/Command.hs -36 +122
    M ./Distribution/Simple/Configure.hs -27 +38
    M ./Distribution/Simple/GHC.hs -6 +6
    M ./Distribution/Simple/Haddock.hs -14 +18
    M ./Distribution/Simple/Install.hs -3 +5
    M ./Distribution/Simple/Register.hs -14 +15
    M ./Distribution/Simple/Setup.hs -442 +875
    M ./Distribution/Simple/SrcDist.hs -2 +4