Proposal: priority queues in containers

[Jim Apple]

> That said, as you
> found, my implementation is still slightly faster when the benchmark is
> corrected.

Well, I only tested one thing (heap sort), and QuickBinom is actually
faster under different options (-prof -auto-all or without calling
performGC before every heapsort).

In either case, though, the speedup is only by a small margin. I think
picking a PQ implementation should be based on a few more benchmarks
under a few more options, but I'm not sure that the decision must be
made now.

Louis, you note later in this email that your implementation is done.
That seems important to me. If we fix a sane interface now, the
implementation can be changed later if we find something more
efficient, right?