Make Tor able to handle VoIP applications people already want to use

One goal we would like to work on for SponsorF year3 is the very hard topic of getting Tor to handle datagram end-to-end -- which may not even be on the roadmap depending on which of Steven's transport approaches we end up liking. An alternative approach would be to make/modify VoIP applications to work better on Tor (#5700 (moved)).