PorcE: Remove old future data as much as is easy.
PorcE: Remove old future data as much as is easy.

This does NOT clean servingRemoteFutures (see TODO).
This change switches to using java HashSet since it allows setting
the initial table size. This significantly reduces the rate of
memory leaking (again see that TODO).

orc-lang/orc,orc-lang/orc,orc-lang/orc,orc-lang/orc,orc-lang/orc