Background: There exists a feature space for queues that extends
between:
* simple, single-ended, non-concurrent, bounded queues
* double-ended, threadsafe, growable queues
... with important points inbetween (such as
the queues used for work-stealing).
This package includes an interface for Deques that allows the
programmer to use a single API for all of the above, while using
the type-system to select an efficient implementation given the
requirements (using type families).
This package also includes a simple reference implementation based
on 'IORef' and "Data.Sequence".
ok jasper@
e52927accc