patch applied (cabal-install): Use mplus not mappend for combining tar filename checks

[Duncan Coutts]

Tue Aug 26 16:26:06 PDT 2008  Duncan Coutts <duncan at haskell.org>
  * Use mplus not mappend for combining tar filename checks
  mappend would join the error messages in the case that both
  checks failed. Also the monoid instance was new in base 3.

    M ./Distribution/Client/Tar.hs -7 +7

View patch online:
http://darcs.haskell.org/cabal-install/_darcs/patches/20080826232606-adfee-f47a7b80993c9a124f20cee1c9ae4144377051e8.gz