Fix previous new-freeze patch for older containers versions
Fix previous new-freeze patch for older containers versions

containers-0.4.x didn't include the mergeWithKey function, so we use a
less efficient method in the 0.4.x case.

themoritz/cabal,sopvop/cabal,themoritz/cabal,sopvop/cabal,mydaum/cabal,mydaum/cabal,themoritz/cabal,sopvop/cabal