Incoming clippy breakage

[phansch]

Once rust-lang/rust#50418 is done, we will have to update clippy: rust-lang/rust#50418 (comment)

All the methods of the Delegate trait will take cmt by reference instead and we have to update the places where we use those methods:

https://github.com/rust-lang-nursery/rust-clippy/blob/f84cc2cc3642d54c69e6a2e7748f9468ade0346f/clippy_lints/src/loops.rs#L1414-L1446

https://github.com/rust-lang-nursery/rust-clippy/blob/c1b39c4551cf5645706d1ddd2925d17271638333/clippy_lints/src/needless_pass_by_value.rs#L369-L395