submodules: update clippy from fc24fce7 to 721f688e#57138

Merged

bors merged 1 commit intorust-lang:masterfrom

matthiaskrgr:clippy

Dec 29, 2018

Commits on Dec 28, 2018

submodules: update clippy from fc24fce7 to f7bdf500
matthiaskrgr
committed