multiple dispatch using run & compile time reflection

[Christian Kamm]

> Neat.

Thanks! Experimenting with the new functionality was fun.

> I gather that since you're using near-trival function bodies for testing,
> these timings represent the relative call
> dispatch overhead?

I hope so. For testing I used empty function bodies (they weren't optimized
away; the empty loop finished significantly faster) and an average over ten
million calls.

It might get worse if there are a lot of overloads, but I don't think by
much.