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devel: Remove SHA1 hashes for distfiles

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Import psqueues-0.2.7.2

The psqueues package provides Priority Search Queues in three
different flavors.

* OrdPSQ k p v, which uses the Ord k instance to provide fast
  insertion, deletion and lookup. This implementation is based on Ralf
  Hinze's A Simple Implementation Technique for Priority Search
  Queues. Hence, it is similar to the PSQueue library, although it is
  considerably faster and provides a slightly different API.

* IntPSQ p v is a far more efficient implementation. It fixes the key
  type to Int and uses a radix tree (like IntMap) with an additional
  min-heap property.

* HashPSQ k p v is a fairly straightforward extension of IntPSQ: it
  simply uses the keys' hashes as indices in the IntPSQ. If there are
  any hash collisions, it uses an OrdPSQ to resolve those. The
  performance of this implementation is comparable to that of IntPSQ,
  but it is more widely applicable since the keys are not restricted
  to Int, but rather to any Hashable datatype.

Each of the three implementations provides the same API, so they can
be used interchangeably. The benchmarks show how they perform relative
to one another, and also compared to the other Priority Search Queue
implementations on Hackage: PSQueue and fingertree-psqueue.