document MIR-based borrowck

[nikomatsakis]

So much to talk about here!

Off the top of my head:

• Dataflow
  • MovePathIndex and that whole setup
• The MIR typeck
• Liveness
• Regions and SCC
• The outlives constraint

[nikomatsakis]

cc @pnkfelix :)

[mark-i-m]

@nikomatsakis I think almost everything here is in the guide or in the TODOs. Do you want to keep this open?

[mark-i-m]

I'm going to go ahead and close this, as much of it is already documented. Please feel free to reopen or file a new issue if something is missing.