Log Message:
devel/hs-mutable-containers: import hs-mutable-containers-0.3.4

One of Haskell's strengths is immutable data structures. These structures
make it easier to reason about code, simplify concurrency and parallelism,
and in some cases can improve performance by allowing sharing. However,
there are still classes of problems where mutable data structures can both
be more convenient, and provide a performance boost. This library is meant
to provide such structures in a performant, well tested way. It also
provides a simple abstraction over such data structures via typeclasses.