patch applied (cabal): Arch and OS names were previously allowed to contain "_-", restore that.

[Duncan Coutts]

Wed Mar 26 17:46:31 PDT 2008  Duncan Coutts <duncan at haskell.org>
  * Arch and OS names were previously allowed to contain "_-", restore that.
  That is the arch and os strings in conditionals in .cabal files, like:
    if arch(x86_64)
  Previously the parser used isAlphaNum c || (c `elem` "_-"). This is
  crucial for arch names like "x86_64". So make the new parser for OS
  and Arch types use the same string parser as before (there is a string
  parse part and a separate classification of known OS/Arch values).

    M ./Distribution/System.hs -5 +6

View patch online:

  http://darcs.haskell.org/cabal/_darcs/patches/20080327004631-adfee-c36a10693a672ccdd950fd19c959d9f788d05afd.gz