Rust support hits linux-next

Depends on who you ask I guess. Is it "clear" when a chain of iterator calls are fused into a single loop over the input? Is it "clear" when tail call optimization is applied? I couldn't tell you what instructions any given line compile down to in Rust or C myself anyways, so for me none of it is "clear" anyways.

That said, I don't know Rust's guarantees around reordering statements, but given the more explicit "I'm using a single variable across threads" model, there are likely a lot fewer ways the compiler can think to order things (barring bugs in the compiler, but that's C's problem too).