Rollup merge of #50344 - SimonSapin:cargo, r=alexcrichton
Rollup merge of #50344 - SimonSapin:cargo, r=alexcrichton

Update Cargo to 2018-04-28 122fd5be5201913d42e219e132d6569493583bca

graydon/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,graydon/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust,GBGamer/rust,aidancully/rust,GBGamer/rust,graydon/rust,GBGamer/rust,graydon/rust,GBGamer/rust,aidancully/rust,aidancully/rust