…y're used instead of once. This is a step on the way to default methods.
The parser now warns about use of mutbl-ref mode, though it's kind of a lie since this commit doesn't remove support for the mode. Changed move_val_init to have stage0 and stage1/2 versions, the latter of which is demoded. Changed the type that the typechecker expects the move_val_init intrinsic to have. After this is pushed, I can make a new snapshot, which will remove the need for the stage0 versions.
One instance remains in net_tcp due to a foreign fn. Lots of instances remain in serialization.rs, but IIRC that is being removed. I had to do unholy things to task-perf-word-count-generic to get it to compile after demoding pipes. I may well have messed up its performance, but it passes.