Feature: RC Immix

[jjl]

paper (PDF)
paper code (java)

this paper's packed full of goodies. in particular,, RC-Immix and RC-Immix (No Proactive Copying) may be of interest, but i also saw your ticket about a conservative collector, so you might enjoy RC-Immix(cons) too.

I'm tempted to implement one or two of these for my toy lisp. If I get around to it, would you be interested in a PR?

[playXE]

@jjl hello! Comet is not maintained now. But I would like to see your implementation of RCImmix in Rust. :)