Proposal: Tidy up and export PSQ from base

[Edward Z. Yang]

Excerpts from Johan Tibell's message of Sun May 01 04:26:52 -0400 2011:
> I just wanted to note that the PSQ was made monomorphic for
> performance reasons (about a 30% improvement) and I be hesitant to use
> a more generic version in the event manager unless it performs close
> to the current implementation.

Just to clarify, here you mean monomorphic in the key and priority values?

Edward