patch applied (ghc-6.6/ghc): Give -fwrapv to gcc when it supports it

[Ian Lynagh]

Mon Jan 15 11:42:50 PST 2007  Ian Lynagh <igloo at earth.li>
  * Give -fwrapv to gcc when it supports it
  Fixes trac #952: Haskell requires consistent overflow behaviour, which
  gcc doesn't give without this flag.

    M ./aclocal.m4 +12
    M ./compiler/main/DriverPipeline.hs +4
    M ./configure.ac +1