Enable -funbox-strict-small-fields by default
See discussion at http://www.haskell.org/pipermail/ghc-devs/2013-April/001109.html
Summary from the commit message:
Enable -funbox-small-strict-fields by default The flag shows no real impact on nofib benchmarks and GHC itself, which is expected given the small number of strict but not already unpacked fields in the source of these programs. However, the flag allows us to omit most of the UNPACK pragmas that are so common in source code today.