Update to rust HEAD
Update to rust HEAD

Ticki/serde,skade/serde,oli-obk/rust-serde,thorbenk/serde,Hoverbear/serde,Byron/serde,infinityb/serde,3Hren/serde,jmesmon/serde,JohnHeitmann/serde,eefriedman/serde,erickt/serde,tempbottle/serde,sidred10/serde,serde-rs/serde,pcwalton/serde,csmulhern/serde