Track down the N23 patch, then update it for modern Tor
This summer, Mashael, Kevin et al published the Defenestrator paper, where they proposed the N23 algorithm to improve Tor's flow control.
They did their simulations using ExperimenTor, and the paper says "we use the latest development branch of the Tor source code (version 0.2.3.0-alpha-dev)".
We should get a copy of their patch, and then update it to apply cleanly to current git.
Then we'll have a common ground for the N23 simulations in #4486 (moved) and #4487 (moved).