patch applied (packages/containers): Do not pass f explicitely for fold.

[Ian Lynagh]

Tue Oct 19 13:20:43 PDT 2010  Milan Straka <fox at ucw.cz>
  * Do not pass f explicitely for fold.
  
  Benchmarks shows this is a huge win (100% for (:) being
  the function, 1000% for (+) being the function).

    M ./Data/IntMap.hs -5 +5
    M ./Data/IntSet.hs -5 +5
    M ./Data/Map.hs -6 +6
    M ./Data/Set.hs -3 +3

View patch online:
http://darcs.haskell.org/cgi-bin/darcsweb.cgi?r=packages/containers;a=darcs_commitdiff;h=20101019202043-7b66e-3ace0def319dd691eea6dde0959fa474fd31e9d5.gz